P
Phosphorous, Polonium, Potassium,
Q
R
Radium, Reaction, Reactant, Roasting,
S
Sodium, Sulphur
T
Titanium, Tritration, Tungsten,
Tuesday, December 23, 2014
Chemistry Concepts Recall P to T
P
Phosphorous, Polonium, Potassium,
Q
R
Radium, Reaction, Reactant, Roasting,
S
Sodium, Sulphur
T
Titanium, Tritration, Tungsten,
Sunday, December 21, 2014
Chemistry Concepts Recall U to Z
U
Uranium,
V
Valence, Valence bond approach. VSEPR Model
W
X
Y
Z
Zerothlaw of thermodynamics
Chemistry Concepts Recall K to O
k
Kossel - Lewis approach to bonding
L
Liquid state
M
Magnesium, Manganese,Mercury, Molybdenum,
N
Nickel,
O
Organic Chemistry, Oxidation, Oxygen,
Chemistry Concepts Recall F to J
F
Fission of a covalent bond, Fundamental particles, Fusion,
G
Gaseous state, Gibbs energy, Graham's law of diffusion or effusion,
H
Hydrogcarbons, Hydrogen
I
Ionization potential
J
IIT JEE Revision - Electrophilic Addition Reactions of Alkenes with X2, HX, HOX and H2O (X=halogen)
Reaction mechanism
Reaction takes place in two steps.
Step 2: The negatively charged atom of the attacking molecule reacts with positively charged carbon of the alkene to complete the formation of addition product.
Electrophilic Addition Reactions of Alkenes with X2, HX, HOX and H2O (X=halogen)
Halogens (particularly chlorine and bromine) react with alkenes in the presence of an inert solvent (e.g. CCl4) to form dihalogen derivatives:
The reaction with flourine is explosive whereas iodine reacts very slowly.
Alkenes react with halogen acids (HCL, HBr, or HI) to form alkyl halides.
In these reactions one part of the molecule attaches itself to one carbon atom of the double bond whereas the other part to the second carbon atom of the double bond.
However,if the alkene is unsymmetrical, then two products are possible depending upon the carbon atom to which the halogen atom is attached.
Markovnikov rule: during the addition across unsymmetrical multiple bond, the negative part of the attacking reagent joins with the carbon atom which carries smaller number of hydrogen atoms while the positive part goes to the carbon atom with more hydrogen atoms.
Due to fact that the reaction proceeds according to Markow(v)nikov's explanation, addition of HBr to Propene gives 2-Bromopropene as the major product up to 90%.
Exception to Markovnikov rule - Kharasch effect - Peroxide effect: During the addition of HBr to an unsymmetrical alkene in the presence of organic peroxids (e.g., benzoyl peroxide), Br atom will join to the carbon carrying more hydrogen atoms while H atom will go to the other carbon atom.
Only HBr shows peroxide effect. HF, HCl and HI do not exhibit peroxide effect.
Alkenes react with hypohalous acids (HOX) or halogen Cl2 or Br2 in the presence of H2O to give halohydrins. In this reactin, markonikov;s rule is followed and halogen is the positive aprtg and OH is the negative part.
Water adds to alkenes in the presence of mineral acids (catalytic hydration of alkenes). Addition occurs in accordance with Markownikov's rule and we get alcohols from this addition.
Ethene gives ethanol
Propene gives Propan-2-ol as the major product.
Reaction takes place in two steps.
Step 1. Attacking molecule gets partially polarised and as it becomes closer to the pi bond of the double bond, the electron cloud of the pi bond repels the electron cloud of the attacking molecule further. As a result, the nearer end of the attacking molecule acquires partial positive charge. At the same time, electromeric effect comes into operation in the double bond and the pi electron pair shifts to one of the carbon atoms making it negatively charged. Thus the partially positively charged atom of the attacking molecule attacks the negatively charged carbon of the alkenes and a new bond is formed. This leaves the other carbon atom with positive charge and also the other atom of the attacking molecule with negative charge.
Step 2: The negatively charged atom of the attacking molecule reacts with positively charged carbon of the alkene to complete the formation of addition product.
Electrophilic Addition Reactions of Alkenes with X2, HX, HOX and H2O (X=halogen)
Halogens (particularly chlorine and bromine) react with alkenes in the presence of an inert solvent (e.g. CCl4) to form dihalogen derivatives:
The reaction with flourine is explosive whereas iodine reacts very slowly.
Alkenes react with halogen acids (HCL, HBr, or HI) to form alkyl halides.
In these reactions one part of the molecule attaches itself to one carbon atom of the double bond whereas the other part to the second carbon atom of the double bond.
However,if the alkene is unsymmetrical, then two products are possible depending upon the carbon atom to which the halogen atom is attached.
Markovnikov rule: during the addition across unsymmetrical multiple bond, the negative part of the attacking reagent joins with the carbon atom which carries smaller number of hydrogen atoms while the positive part goes to the carbon atom with more hydrogen atoms.
Due to fact that the reaction proceeds according to Markow(v)nikov's explanation, addition of HBr to Propene gives 2-Bromopropene as the major product up to 90%.
Exception to Markovnikov rule - Kharasch effect - Peroxide effect: During the addition of HBr to an unsymmetrical alkene in the presence of organic peroxids (e.g., benzoyl peroxide), Br atom will join to the carbon carrying more hydrogen atoms while H atom will go to the other carbon atom.
Only HBr shows peroxide effect. HF, HCl and HI do not exhibit peroxide effect.
Alkenes react with hypohalous acids (HOX) or halogen Cl2 or Br2 in the presence of H2O to give halohydrins. In this reactin, markonikov;s rule is followed and halogen is the positive aprtg and OH is the negative part.
Water adds to alkenes in the presence of mineral acids (catalytic hydration of alkenes). Addition occurs in accordance with Markownikov's rule and we get alcohols from this addition.
Ethene gives ethanol
Propene gives Propan-2-ol as the major product.
21 December - Chemistry Knowledge History
John Mayow baptized 1641 (birth date uncertain): discovered that air contained two gases, one of which ("spiritus nitro-aerous") supported life and combustion.
Hermann Joseph Muller born 1890: theory of genes; mutation by X-rays; Nobel Prize (medicine), 1946.
December - Chemistry Knowledge History
John Mayow's Scientific Work
Mayow published at Oxford in 1668 two tracts, on respiration and rickets,
Accepting Boyle's experiments and theory that air is necessary for combustion, Mayow showed that fire is supported not by the air as a whole but by a more active and subtle part of it. This part he called "spiritus igneo-aereus," or sometimes "nitro-aereus", In combustion the nitro-aereae supplied by the air combined with the material burnt. Mayow observed that antimony, strongly heated with a burning glass, undergoes an increase of weight and he attributed it to nothing else but these particles.
Mayow argued that the same particles are consumed in respiration, because he found that when a small animal and a lighted candle were placed in a closed vessel full of air the candle first went out and soon afterwards the animal died. However, if there was no candle present the animal lived twice as long. He concluded that this constituent of the air is absolutely necessary for life, and supposed that the lungs separate it from the atmosphere and pass it into the blood. Mayow also came out with the idea that muscles work or contract due to combination of nitro aereus with other combustible (salino-sulphureous) particles in the body; hence the heart, being a muscle, ceases to beat when respiration is stopped. Heat in animals is due to the union of nitro-aerial particles, breathed in from the air, with the combustible particles in the blood, and it occurs in muscles during violent exertions.
In effect, therefore, Mayow gave a remarkably correct anatomical description of the mechanism of respiration and argued for the existence of oxygen, under the guise of his "spiritus nitro-aereus," as a separate entity distinct from the general mass of the air. Mayow perceived the part "spiritus nitro-aereus" plays in combustion and in increasing the weight of the calces (oxides) of metals as compared with metals themselves. Mayow described inspiration a mechanism for introducing oxygen into the body, where it is consumed for the production of heat and muscular activity. He even vaguely conceived of expiration as an excretory process. Using bell-jars over water Mayow showed that the active substance - nitro-aereus that we today call oxygen constitutes about a fifth part of the air.
http://en.wikipedia.org/wiki/John_Mayow
Mutation of genes
Genes mutate due to thermal agitations. One gene may mutate but others around may remain stable.
Therefore high energy radiation can produe gene mutations.
Read Muller's Nobel Lecture on Mutation of Genes
http://www.nobelprize.org/nobel_prizes/medicine/laureates/1946/muller-lecture.html
December Month Chemistry Knowledge History
Saturday, December 20, 2014
22 December - Chemistry Knowledge History
Vladimir Markovnikov born 1838: synthesis of cyclobutane and cyclopentane derivatives; Markovnikov's rule for additions to alkenes.
William Lloyd Evans born 1870: chemistry of carbohydrates;
John Clarke Slater born 1900: orbital approaches to quantum chemistry (Slater-type orbitals, Slater determinant); tetrahedral carbon compounds.
Arie Jan Haagen-Smit born 1900: nature and source of smog; smog abatement.
Markovnikov's rule for additions to alkenes.
When the alkene which is unsymmetrical reacts with halogen acid, two products are possible depending upon the carbon atom to which the halogen atom is attached.
Markovnikov rule: during the addition across unsymmetrical multiple bond, the negative part of the attacking reagent joins with the carbon atom which carries smaller number of hydrogen atoms while the positive part goes to the carbon atom with more hydrogen atoms.
Due to fact that the reaction proceeds according to Markow(v)nikov's explanation, addition of HBr to Propene gives 2-Bromopropene as the major product up to 90%.
Exception to Markovnikov rule - Kharasch effect - Peroxide effect: During the addition of HBr to an unsymmetrical alkene in the presence of organic peroxids (e.g., benzoyl peroxide), Br atom will join to the carbon carrying more hydrogen atoms while H atom will go to the other carbon atom.
Propene + HBR in the presence of Benzoyl peroxide gives 1-Bromopropane.
William Lloyd Evans born 1870: chemistry of carbohydrates;
John Clarke Slater born 1900: orbital approaches to quantum chemistry (Slater-type orbitals, Slater determinant); tetrahedral carbon compounds.
Arie Jan Haagen-Smit born 1900: nature and source of smog; smog abatement.
Markovnikov's rule for additions to alkenes.
When the alkene which is unsymmetrical reacts with halogen acid, two products are possible depending upon the carbon atom to which the halogen atom is attached.
Markovnikov rule: during the addition across unsymmetrical multiple bond, the negative part of the attacking reagent joins with the carbon atom which carries smaller number of hydrogen atoms while the positive part goes to the carbon atom with more hydrogen atoms.
Due to fact that the reaction proceeds according to Markow(v)nikov's explanation, addition of HBr to Propene gives 2-Bromopropene as the major product up to 90%.
Exception to Markovnikov rule - Kharasch effect - Peroxide effect: During the addition of HBr to an unsymmetrical alkene in the presence of organic peroxids (e.g., benzoyl peroxide), Br atom will join to the carbon carrying more hydrogen atoms while H atom will go to the other carbon atom.
Propene + HBR in the presence of Benzoyl peroxide gives 1-Bromopropane.
Chemistry Concepts Recall A to E
Try you recall these concepts and refresh your subject
A
Acid, Acid strength, Activity series, Acyllation, Addition reaction, Adsorption, Alkali, Alcohol, Alkali metal, Alkaline earth metal, Aldehyde, Alkane, Alkene, Alkyne, Alkyl radical, Alkenyl radical, Alloy, Allotrope, Aliphatic hydrocarbons, Aliphatic amino acids, Allyl radical, Amalgam, Amides, Amines, Amino acid, Anhydride, Anion, Aromatic compound, Aromaticity, Arenes, Atom, Atomic mass, Atomic number
B
Base, Base strength, Binary compound, Bond, Bond angle, Bond distance, Bond energy, Bobnd polarity, Bond strength, Boyles' law, Bromination, Bronsted-Lowry's theories, Brownian movement
C
catalyst, catalitic distillation, cation, chain reaction, charles' law, chemical equilibrium, chemical kinetics, Cis isomer, Colligative property, combustion, concentration, condensation, Configuration isomer, conformation isomer, coordinate covalent bond copolymer, core electrons, covalent compound, Covalent bond, cracking, crystal, crystal shapes, crystallization
D
Dalton’s law of partial pressures, Deamination, Decane, Decomposition reactions, Delocalised pi bond, Detection of radiation, Differentiating electron, Diffusion of gases, Dipole, Dipole attraction, Displacement reactions, Disproportination, Dissociation coefficients of complex ions, dissolving precipitates, Distillation, Double bond, Double displacement reactions, dsp^3 hybrid orbitals, d^2sp^3 hybrid orbitals
E
Efflorescence, Photoelectric effect, Einsteinium, Electric charge, Electric potential, Electric current, Electrode potential, Electrolysis, Electrolyte,
Eleectromagentic radiation, Electromotive force (EMF), Electron-dot structure, Electronegativity, Electronic structure, Electron sea theory of metals, Electroplating, Electrovalent bond, Empirical formuala, Emulsion, Endothermic chemical raction, Energy level diagram, Enthalpy, Equilibrium constant, Equilibrium shifts, Equivalence point, Ester, Ether, Europium, Exothermic chemical reaction,
A
Acid, Acid strength, Activity series, Acyllation, Addition reaction, Adsorption, Alkali, Alcohol, Alkali metal, Alkaline earth metal, Aldehyde, Alkane, Alkene, Alkyne, Alkyl radical, Alkenyl radical, Alloy, Allotrope, Aliphatic hydrocarbons, Aliphatic amino acids, Allyl radical, Amalgam, Amides, Amines, Amino acid, Anhydride, Anion, Aromatic compound, Aromaticity, Arenes, Atom, Atomic mass, Atomic number
B
Base, Base strength, Binary compound, Bond, Bond angle, Bond distance, Bond energy, Bobnd polarity, Bond strength, Boyles' law, Bromination, Bronsted-Lowry's theories, Brownian movement
C
catalyst, catalitic distillation, cation, chain reaction, charles' law, chemical equilibrium, chemical kinetics, Cis isomer, Colligative property, combustion, concentration, condensation, Configuration isomer, conformation isomer, coordinate covalent bond copolymer, core electrons, covalent compound, Covalent bond, cracking, crystal, crystal shapes, crystallization
D
Dalton’s law of partial pressures, Deamination, Decane, Decomposition reactions, Delocalised pi bond, Detection of radiation, Differentiating electron, Diffusion of gases, Dipole, Dipole attraction, Displacement reactions, Disproportination, Dissociation coefficients of complex ions, dissolving precipitates, Distillation, Double bond, Double displacement reactions, dsp^3 hybrid orbitals, d^2sp^3 hybrid orbitals
E
Efflorescence, Photoelectric effect, Einsteinium, Electric charge, Electric potential, Electric current, Electrode potential, Electrolysis, Electrolyte,
Eleectromagentic radiation, Electromotive force (EMF), Electron-dot structure, Electronegativity, Electronic structure, Electron sea theory of metals, Electroplating, Electrovalent bond, Empirical formuala, Emulsion, Endothermic chemical raction, Energy level diagram, Enthalpy, Equilibrium constant, Equilibrium shifts, Equivalence point, Ester, Ether, Europium, Exothermic chemical reaction,
Friday, December 19, 2014
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Einsteinium - Element - Atomic Number 99
Einsteinium was first identified in December 1952 by Albert Ghiorso and co-workers at the University of California, Berkeley in collaboration with the Argonne and Los Alamos National Laboratories, in the fallout from the Ivy Mike nuclear test.
Ghiorso and co-workers analyzed filter papers which had been flown through the explosion cloud on airplanes (the same sampling technique that had been used to discover 244
94Pu). Larger amounts of radioactive material were later isolated from coral debris of the atoll, which were delivered to the U.S. The separation of suspected new elements was carried out in the presence of a citric acid/ammonium buffer solution in a weakly acidic medium (pH ≈ 3.5), using ion exchange at elevated temperatures; fewer than 200 atoms of einsteinium were recovered in the end.
Nevertheless, element 99 (einsteinium), namely its 253Es isotope, could be detected via its characteristic high-energy alpha decay at 6.6 MeV. It was produced by the capture of 15 neutrons by uranium-238 nuclei followed by seven beta-decays, and had a half-life of 20.5 days.
Later, isotopes of element 99 (as well as of new element 100, fermium) were produced in the Berkeley and Argonne laboratories, in a nuclear reaction between nitrogen-14 and uranium-238, and later by intense neutron irradiation of plutonium or californium:
These results were published in several articles in 1954 with the disclaimer that these were not the first studies that had been carried out on the elements. The Berkeley team also reported some results on the chemical properties of einsteinium and fermium.
In their discovery of the elements 99 and 100, the American teams had competed with a group at the Nobel Institute for Physics, Stockholm, Sweden. In late 1953 – early 1954, the Swedish group succeeded in the synthesis of light isotopes of element 100, in particular 250Fm, by bombarding uranium with oxygen nuclei. These results were also published in 1954. Nevertheless, the priority of the Berkeley team was generally recognized, as its publications preceded the Swedish article, and they were based on the previously undisclosed results of the 1952 thermonuclear explosion; thus the Berkeley team was given the privilege to name the new elements. The official names suggested by the Berkeley group derived from two prominent scientists, Albert Einstein and Enrico Fermi: The discovery of these new elements was announced by Albert Ghiorso at the first Geneva Atomic Conference held on 8–20 August 1955. The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC.
Characteristics
Einsteinium is a synthetic, silvery-white, radioactive metal. In the periodic table, it is located to the right of the actinide californium, to the left of the actinide fermium and below the lanthanide holmium with which it shares many similarities in physical and chemical properties. Its density of 8.84 g/cm3 is lower than that of californium (15.1 g/cm3) and is nearly the same as that of holmium (8.79 g/cm3), despite atomic einsteinium being much heavier than holmium. The melting point of einsteinium (860 °C) is also relatively low – below californium (900 °C), fermium (1527 °C) and holmium (1461 °C). Einsteinium is a soft metal, with the bulk modulus of only 15 GPa, which value is one of the lowest among non-alkali metals.
The metal is divalent and has a noticeably high volatility.
Magnetic properties have been studied for einsteinium metal, its oxide and fluoride. All three materials showed Curie–Weiss paramagnetic behavior from liquid helium to room temperature. The effective magnetic moments were deduced as 10.4 ± 0.3 µB for Es2O3 and 11.4 ± 0.3 µB for the EsF3, which are the highest values among actinides, and the corresponding Curie temperatures are 53 and 37 K.
Chemical
Like all actinides, einsteinium is rather reactive. Its trivalent oxidation state is most stable in solids and aqueous solution where it induced pale pink color. The existence of divalent einsteinium is firmly established, especially in solid phase; such +2 state is not observed in many other actinides, including protactinium, uranium, neptunium, plutonium, curium and berkelium. Einsteinium(II) compounds can be obtained, for example, by reducing einsteinium(III) with samarium(II) chloride. The oxidation state +4 was postulated from vapor studies and is yet uncertain.
Isotopes
Nineteen nuclides and three nuclear isomers are known for einsteinium with atomic weights ranging from 240 to 258. All are radioactive and the most stable nuclide, 252Es, has a half-life of 471.7 days.[ Next most stable isotopes are 254Es (half-life 275.7 days), 255Es (39.8 days) and 253Es (20.47 days). All of the remaining isotopes have half-lives shorter than 40 hours, and most of them decay within less than 30 minutes. Of the three nuclear isomers, the most stable is 254mEs with half-life of 39.3 hours.
Synthesis and extraction
Einsteinium is produced in minute quantities by bombarding lighter actinides with neutrons in dedicated high-flux nuclear reactors. The world's major irradiation sources are the 85-megawatt High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory in Tennessee, U.S., and the SM-2 loop reactor at the Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad, Russia,which are both dedicated to the production of transcurium (Z > 96) elements. These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements, although the quantities produced at NIIAR are not widely reported. In a "typical processing campaign" at Oak Ridge, tens of grams of curium are irradiated to produce decigram quantities of californium, milligram quantities of berkelium (249Bk) and einsteinium and picogram quantities of fermium.
The first microscopic sample of 253Es sample weighing about 10 nanograms was prepared in 1961 at HFIR. Larger batches were produced later starting from several kilograms of plutonium with the einsteinium yields (mostly 253Es) of 0.48 milligrams in 1967–1970, 3.2 milligrams in 1971–1973, followed by steady production of about 3 milligrams per year between 1974 and 1978. These quantities however refer to the integral amount in the target right after irradiation. Subsequent separation procedures reduced the amount of isotopically pure einsteinium roughly tenfold.
Heavy neutron irradiation of plutonium results in four major isotopes of einsteinium: 253Es (α-emitter with half-life of 20.03 days and with a spontaneous fission half-life of 7×105 years); 254mEs (β-emitter with half-life of 38.5 hours), 254Es (α-emitter with half-life of about 276 days) and 255Es (β-emitter with half-life of 24 days). An alternative route involves bombardment of uranium-238 with high-intensity nitrogen or oxygen ion beams.
Einsteinium-247 (half-life 4.55 minutes) was produced by irradiating americium-241 with carbon or uranium-238 with nitrogen ions. The latter reaction was first realized in 1967 in Dubna, Russia, and the involved scientists were awarded the Lenin Komsomol Prize.
The isotope 248Es was produced by irradiating 249Cf with deuterium ions. It mainly decays by emission of electrons to 248Cf with a half-life of 25 (±5) minutes, but also releases α-particles of 6.87 MeV energy, with the ratio of electrons to α-particles of about 400.
The heavier isotopes 249Es, 250Es, 251Es and 252Es were obtained by bombarding 249Bk with α-particles. One to four neutrons are liberated in this process making possible the formation of four different isotopes in one reaction.
Einsteinium-253 was produced by irradiating a 0.1–0.2 milligram 252Cf target with a thermal neutron flux of (2–5)×1014 neutrons·cm−2·s−1 for 500–900 hours:[64]
A personal account by Ghiorso
Ghiorso and co-workers analyzed filter papers which had been flown through the explosion cloud on airplanes (the same sampling technique that had been used to discover 244
94Pu). Larger amounts of radioactive material were later isolated from coral debris of the atoll, which were delivered to the U.S. The separation of suspected new elements was carried out in the presence of a citric acid/ammonium buffer solution in a weakly acidic medium (pH ≈ 3.5), using ion exchange at elevated temperatures; fewer than 200 atoms of einsteinium were recovered in the end.
Nevertheless, element 99 (einsteinium), namely its 253Es isotope, could be detected via its characteristic high-energy alpha decay at 6.6 MeV. It was produced by the capture of 15 neutrons by uranium-238 nuclei followed by seven beta-decays, and had a half-life of 20.5 days.
Later, isotopes of element 99 (as well as of new element 100, fermium) were produced in the Berkeley and Argonne laboratories, in a nuclear reaction between nitrogen-14 and uranium-238, and later by intense neutron irradiation of plutonium or californium:
These results were published in several articles in 1954 with the disclaimer that these were not the first studies that had been carried out on the elements. The Berkeley team also reported some results on the chemical properties of einsteinium and fermium.
In their discovery of the elements 99 and 100, the American teams had competed with a group at the Nobel Institute for Physics, Stockholm, Sweden. In late 1953 – early 1954, the Swedish group succeeded in the synthesis of light isotopes of element 100, in particular 250Fm, by bombarding uranium with oxygen nuclei. These results were also published in 1954. Nevertheless, the priority of the Berkeley team was generally recognized, as its publications preceded the Swedish article, and they were based on the previously undisclosed results of the 1952 thermonuclear explosion; thus the Berkeley team was given the privilege to name the new elements. The official names suggested by the Berkeley group derived from two prominent scientists, Albert Einstein and Enrico Fermi: The discovery of these new elements was announced by Albert Ghiorso at the first Geneva Atomic Conference held on 8–20 August 1955. The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC.
Characteristics
Einsteinium is a synthetic, silvery-white, radioactive metal. In the periodic table, it is located to the right of the actinide californium, to the left of the actinide fermium and below the lanthanide holmium with which it shares many similarities in physical and chemical properties. Its density of 8.84 g/cm3 is lower than that of californium (15.1 g/cm3) and is nearly the same as that of holmium (8.79 g/cm3), despite atomic einsteinium being much heavier than holmium. The melting point of einsteinium (860 °C) is also relatively low – below californium (900 °C), fermium (1527 °C) and holmium (1461 °C). Einsteinium is a soft metal, with the bulk modulus of only 15 GPa, which value is one of the lowest among non-alkali metals.
The metal is divalent and has a noticeably high volatility.
Magnetic properties have been studied for einsteinium metal, its oxide and fluoride. All three materials showed Curie–Weiss paramagnetic behavior from liquid helium to room temperature. The effective magnetic moments were deduced as 10.4 ± 0.3 µB for Es2O3 and 11.4 ± 0.3 µB for the EsF3, which are the highest values among actinides, and the corresponding Curie temperatures are 53 and 37 K.
Chemical
Like all actinides, einsteinium is rather reactive. Its trivalent oxidation state is most stable in solids and aqueous solution where it induced pale pink color. The existence of divalent einsteinium is firmly established, especially in solid phase; such +2 state is not observed in many other actinides, including protactinium, uranium, neptunium, plutonium, curium and berkelium. Einsteinium(II) compounds can be obtained, for example, by reducing einsteinium(III) with samarium(II) chloride. The oxidation state +4 was postulated from vapor studies and is yet uncertain.
Isotopes
Nineteen nuclides and three nuclear isomers are known for einsteinium with atomic weights ranging from 240 to 258. All are radioactive and the most stable nuclide, 252Es, has a half-life of 471.7 days.[ Next most stable isotopes are 254Es (half-life 275.7 days), 255Es (39.8 days) and 253Es (20.47 days). All of the remaining isotopes have half-lives shorter than 40 hours, and most of them decay within less than 30 minutes. Of the three nuclear isomers, the most stable is 254mEs with half-life of 39.3 hours.
Synthesis and extraction
Einsteinium is produced in minute quantities by bombarding lighter actinides with neutrons in dedicated high-flux nuclear reactors. The world's major irradiation sources are the 85-megawatt High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory in Tennessee, U.S., and the SM-2 loop reactor at the Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad, Russia,which are both dedicated to the production of transcurium (Z > 96) elements. These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements, although the quantities produced at NIIAR are not widely reported. In a "typical processing campaign" at Oak Ridge, tens of grams of curium are irradiated to produce decigram quantities of californium, milligram quantities of berkelium (249Bk) and einsteinium and picogram quantities of fermium.
The first microscopic sample of 253Es sample weighing about 10 nanograms was prepared in 1961 at HFIR. Larger batches were produced later starting from several kilograms of plutonium with the einsteinium yields (mostly 253Es) of 0.48 milligrams in 1967–1970, 3.2 milligrams in 1971–1973, followed by steady production of about 3 milligrams per year between 1974 and 1978. These quantities however refer to the integral amount in the target right after irradiation. Subsequent separation procedures reduced the amount of isotopically pure einsteinium roughly tenfold.
Heavy neutron irradiation of plutonium results in four major isotopes of einsteinium: 253Es (α-emitter with half-life of 20.03 days and with a spontaneous fission half-life of 7×105 years); 254mEs (β-emitter with half-life of 38.5 hours), 254Es (α-emitter with half-life of about 276 days) and 255Es (β-emitter with half-life of 24 days). An alternative route involves bombardment of uranium-238 with high-intensity nitrogen or oxygen ion beams.
Einsteinium-247 (half-life 4.55 minutes) was produced by irradiating americium-241 with carbon or uranium-238 with nitrogen ions. The latter reaction was first realized in 1967 in Dubna, Russia, and the involved scientists were awarded the Lenin Komsomol Prize.
The isotope 248Es was produced by irradiating 249Cf with deuterium ions. It mainly decays by emission of electrons to 248Cf with a half-life of 25 (±5) minutes, but also releases α-particles of 6.87 MeV energy, with the ratio of electrons to α-particles of about 400.
The heavier isotopes 249Es, 250Es, 251Es and 252Es were obtained by bombarding 249Bk with α-particles. One to four neutrons are liberated in this process making possible the formation of four different isotopes in one reaction.
Einsteinium-253 was produced by irradiating a 0.1–0.2 milligram 252Cf target with a thermal neutron flux of (2–5)×1014 neutrons·cm−2·s−1 for 500–900 hours:[64]
A personal account by Ghiorso
Thursday, December 18, 2014
Chapter 17 Co-Ordination Compounds - JEE Main Chemistry
17 Co-Ordination Compounds
Introduction to co-ordination compounds, Werner’s theory; ligands, coordination number, denticity,
chelation; IUPAC nomenclature of mononuclear coordination compounds, isomerism; Bonding-Valence bond approach and basic ideas of Crystal field theory, colour and magnetic properties; Importance of coordination compounds (in qualitative analysis, extraction of metals and in biological systems).
Questions
1. Which of the following exists as covalent crystals in the solid state ?
(1) Iodine (2) Silicon (3) Sulphur (4) Phosphorus (2013)
Answer (2)
Silicon exists as covalent crystals in the solid state.
Introduction to Coordination Compounds
Introduction to co-ordination compounds, Werner’s theory; ligands, coordination number, denticity,
chelation; IUPAC nomenclature of mononuclear coordination compounds, isomerism; Bonding-Valence bond approach and basic ideas of Crystal field theory, colour and magnetic properties; Importance of coordination compounds (in qualitative analysis, extraction of metals and in biological systems).
Questions
1. Which of the following exists as covalent crystals in the solid state ?
(1) Iodine (2) Silicon (3) Sulphur (4) Phosphorus (2013)
Answer (2)
Silicon exists as covalent crystals in the solid state.
Introduction to Coordination Compounds
Redox Reactions And Electrochemistry - JEE Main Chemistry Chapter 8
8 Redox Reactions And Electrochemistry
Electronic concepts of oxidation and reduction, redox reactions, oxidation number, rules for assigning
oxidation number, balancing of redox reactions. Eectrolytic and metallic conduction, conductance in
electrolytic solutions, specific and molar conductivities and their variation with concentration: Kohlrausch’s law and its applications.
Electrochemical cells - Electrolytic and Galvanic cells, different types of electrodes, electrode potentials including standard electrode potential, half - cell and cell reactions, emf of a Galvanic cell and its measurement; Nernst equation and its applications; Relationship between cell potential and Gibbs’ energy change; Dry cell and lead accumulator; Fuel cells.
Redox Reactions - Bozeman Science
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Khan Academy - Redox Reactions
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Electronic concepts of oxidation and reduction, redox reactions, oxidation number, rules for assigning
oxidation number, balancing of redox reactions. Eectrolytic and metallic conduction, conductance in
electrolytic solutions, specific and molar conductivities and their variation with concentration: Kohlrausch’s law and its applications.
Electrochemical cells - Electrolytic and Galvanic cells, different types of electrodes, electrode potentials including standard electrode potential, half - cell and cell reactions, emf of a Galvanic cell and its measurement; Nernst equation and its applications; Relationship between cell potential and Gibbs’ energy change; Dry cell and lead accumulator; Fuel cells.
Redox Reactions - Bozeman Science
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Khan Academy - Redox Reactions
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JEE Main Chemistry - Chapter 12. General Principles And Processes Of Isolation Of Metals
12 General Principles And Processes Of Isolation Of Metals
Modes of occurrence of elements in nature, minerals, ores;
Steps involved in the extraction of metals - concentration, reduction (chemical and electrolytic
methods) and refining with special reference to the extraction of Al, Cu, Zn and Fe;
Thermodynamic and electrochemical principles involved in the extraction of metals.
Self Reduction of Copper
Carbon Reduction Method
Electrolytic reduction method
JEE Main Chemistry 2015 Syllabus
JEE Main Chemistry Syllabus Study Plan and Revision Notes:
Basic Concepts of Chemistry,
Study Guide - Notes
States of Matter,
Study Guide - Notes
Atomic Structure,
Class XI Portion Study Guide - Notes
Chemical Bonding and Molecular Structure,
Study Guide - Notes
Chemical Thermodynamics,
Study Guide - Notes
Solutions,
Study Guide - Notes
Equilibrium,
Study Guide - Notes
Redox Reactions and Electrochemistry
Study Guide - Notes
Chemical Kinetics,
Study Guide - Notes
Surface Chemistry,
Study Guide - Notes
Classification of Elements and Periodicity in Properties,
Study Guide - Notes
General Principles and Process of isolation of Metals,
Study Guide - Notes
Hydrogen,
Study Guide - Notes
S, P, D and F Block Elements,
Study Guide - Notes
Co-ordination Compounds,
Study Guide - Notes
Environmental Chemistry,
Study Guide - Notes
Purification and characteristics of organic compounds,
some basic principles of organic chemistry,
Study Guide - Notes
Hydrocarbons,
Study Guide - Notes
Organic Compounds Containing Halogens,
Study Guide - Notes
Organic Compounds containing oxygen,
Study Guide - Notes
Polymers,
Study Guide - Notes
Bio-molecules,
Study Guide - Notes
Chemistry in Daily Life and Principles related to piratical chemistry.
Study Guide - Notes
Detailed Syllabus
JEE MAIN 2015 DETAILED SYLLABUS FOR CHEMISTRY:
Section A: Physical Chemistry
1 Some Basic Concepts in Chemistry
Matter and its nature, Dalton’s atomic theory; Concept of atom, molecule, element and compound; Physical quantities and their measurements in Chemistry, precision and accuracy, significant figures, S.I. Units, dimensional analysis; Laws of chemical combination; Atomic and molecular masses, mole concept, molar mass, percentage composition, empirical and molecular formulae; Chemical equations and stoichiometry.
2 States of Matter
Classification of matter into solid, liquid and gaseous states
Gaseous State: Measurable properties of gases; Gas laws - Boyle’s law, Charle’s law, Graham’s law of diffusion, Avogadro’s law, Dalton’s law of partial pressure; Concept of Absolute scale of temperature; Ideal gas equation; Kinetic theory of gases (only postulates); Concept of average, root
mean square and most probable velocities; Real gases, deviation from Ideal behaviour, compressibility factor and van der Waals equation.
Liquid State: Properties of liquids - vapour pressure, viscosity and surface tension and effect of temperature on them (qualitative treatment only).
Solid State: Classification of solids: molecular, ionic, covalent and metallic solids, amorphous and crystalline solids (elementary idea); Bragg’s Law and its applications; Unit cell and lattices, packing in solids (fcc, bcc and hcp lattices), voids, calculations involving unit cell parameters, imperfection in solids; Electrical, magnetic and dielectric properties.
3 Atomic Structure
Thomson and Rutherford atomic models and their limitations; Nature of electromagnetic radiation,
photoelectric effect; Spectrum of hydrogen atom, Bohr model of hydrogen atom - its postulates, derivation of the relations for energy of the electron and radii of the different orbits, limitations of Bohr’s model; Dual nature of matter, de-Broglie’s relationship, Heisenberg uncertainty principle. Elementary ideas of quantum mechanics, quantum mechanical model of atom, its important features, concept of atomic orbitals as one electron wave functions; Variation of y and y 2 , with r for
1s and 2s orbitals; various quantum numbers (principal, angular momentum and magnetic quantum numbers) and their significance; shapes of s, p and d - orbitals, electron spin and spin quantum number; Rules for filling electrons in orbitals – aufbau principle, Pauli’s exclusion principle and Hund’s rule, electronic configuration of elements, extra stability of half-filled and completely filled orbitals.
4 Chemical Bonding And Molecular Strucure
Kossel - Lewis approach to chemical bond formation, concept of ionic and covalent bonds.
Ionic Bonding: Formation of ionic bonds, factors affecting the formation of ionic bonds;
calculation of lattice enthalpy. Covalent Bonding: Concept of electronegativity, Fajan’s rule, dipole moment; Valence Shell Electron Pair Repulsion (VSEPR) theory and shapes of simple molecules.
Quantum mechanical approach to covalent bonding:
Valence bond theory – Its important features, concept of hybridization involving s, p and d orbitals; Resonance.
Molecular Orbital Theory - Its important features, LCAOs, types of molecular orbitals (bonding,
antibonding), sigma and pi-bonds, molecular orbital electronic configurations of homonuclear diatomic molecules, concept of bond order, bond length and bond energy. Elementary idea of metallic bonding. Hydrogen bonding and its applications
5 Chemical Thermodynamics Fundamentals of thermodynamics: System and surroundings, extensive and intensive properties, state functions, types of processes.
First law of thermodynamics - Concept of work, heat internal energy and enthalpy, heat capacity, molar heat capacity; Hess’s law of constant heat summation; Enthalpies of bond dissociation, combustion, formation, atomization, sublimation, phase transition, hydration, ionization and solution.
Second law of thermodynamics; Spontaneity of processes; DS of the universe and DG of the system as criteria for spontaneity, DG0 (Standard Gibbs energy change) and equilibrium constant.
6 Solutions
Different methods for expressing concentration of solution - molality, molarity, mole fraction, percentage (by volume and mass both), vapour pressure of
solutions and Raoult’s Law – Ideal and non-ideal solutions, vapour pressure - composition, plots for ideal and nonideal solutions; Colligative properties of dilute solutions - relative lowering of vapour pressure, depression of freezing point, elevation of boiling point and osmotic pressure; Determination of molecular mass using colligative properties; Abnormal value of molar mass, van’t Hoff factor and its significance.
7 Equilibrium
Meaning of equilibrium, concept of dynamic equilibrium. Equilibria involving physical processes: Solid -liquid, liquid - gas and solid – gas equilibria, Henry’s law, general characterics of equilibrium involving physical processes.
Equilibria involving chemical processes: Law of chemical equilibrium, equilibrium constants (Kp and Kc) and their significance, significance of DG and DGo in chemical equilibria, factors affecting equilibrium concentration, pressure, temperature, effect of catalyst; Le Chatelier’s principle.
Ionic equilibrium: Weak and strong electrolytes, ionization of electrolytes, various concepts of acids and bases (Arrhenius, Brnsted - Lowry and Lewis) and their ionization, acid - base equilibria (including multistage ionization) and ionization constants, ionization of water, pH scale, common ion effect, hydrolysis of salts and pH of their solutions, solubility of sparingly soluble salts and solubility products, buffer solutions.
8 Redox Reactions And Electrochemistry
Electronic concepts of oxidation and reduction, redox reactions, oxidation number, rules for assigning
oxidation number, balancing of redox reactions. Eectrolytic and metallic conduction, conductance in
electrolytic solutions, specific and molar conductivities and their variation with concentration: Kohlrausch’s law and its applications.
Electrochemical cells - Electrolytic and Galvanic cells, different types of electrodes, electrode potentials including standard electrode potential, half - cell and cell reactions, emf of a Galvanic cell and its measurement; Nernst equation and its applications; Relationship between cell potential and Gibbs’ energy change; Dry cell and lead accumulator; Fuel cells.
9 Chemical Kinetics
Rate of a chemical reaction, factors affecting the rate of reactions: concentration, temperature, pressure and catalyst; elementary and complex reactions, order and molecularity of reactions, rate law, rate constant and its units, differential and integral forms of zero and first order reactions, their characteristics and half - lives, effect of temperature on rate of reactions – Arrhenius theory, activation energy and its calculation, collision theory of bimolecular gaseous reactions (no
derivation).
10 Surface Chemistry
Absorption- Physisorption and chemisorption and their characteristics, factors affecting absorption of gases on solids - Freundlich and Langmuir absorption isotherms, absorption from solutions.
Colloidal state - distinction among true solutions, colloids and suspensions, classification of colloids -
lyophilic, lyophobic; multi molecular, macromolecular and associated colloids (micelles), preparation and properties of colloids - Tyndall effect, Brownian movement, electrophoresis, dialysis, coagulation and flocculation; Emulsions and their characteristics.
Section – B : Inorganic Chemistry
11 Classificaton Of Elements And Periodicity In Properties
Modem periodic law and present form of the periodic table, s, p, d and f block elements, periodic trends in properties of elements atomic and ionic radii, ionization enthalpy, electron gain enthalpy, valence, oxidation states and chemical reactivity
12 General Principles And Processes Of Isolation Of Metals
Modes of occurrence of elements in nature, minerals, ores;
Steps involved in the extraction of metals - concentration, reduction (chemical and electrolytic
methods) and refining with special reference to the extraction of Al, Cu, Zn and Fe;
Thermodynamic and electrochemical principles involved in the extraction of metals.
13 Hydrogen
Position of hydrogen in periodic table, isotopes, preparation, properties and uses of hydrogen; Physical and chemical properties of water and heavy water; Structure, preparation, reactions and uses of hydrogen peroxide; Hydrogen as a fuel.
14. S - Block Elements (Alkali And Alkaline Earth Metals)
Group - 1 and 2 Elements
General introduction, electronic configuration and general trends in physical and chemical properties of elements, anomalous properties of the first element of each group, diagonal relationships. Preparation and properties of some important compounds - sodium carbonate and sodium hydroxide; Industrial uses of lime, limestone, Plaster of Paris and cement; Biological significance of Na, K, Mg and Ca.
15. P - Block Elements Group - 13 to Group 18 Elements
General Introduction: Electronic configuration and general trends in physical and chemical properties of elements across the periods and down the groups; unique behaviour of the first element in each group.
Groupwise study of the p – block elements
Group – 13
Preparation, properties and uses of boron and aluminium; properties of boric acid, diborane, boron
trifluoride, aluminium chloride and alums.
Group – 14
Allotropes of carbon, tendency for catenation; Structure & properties of silicates, and zeolites.
Group – 15
Properties and uses of nitrogen and phosphorus; Allotrophic forms of phosphorus; Preparation, properties, structure and uses of ammonia, nitric acid, phosphine and phosphorus halides, (PCl3, PCl5); Structures of oxides and oxoacids of phosphorus.
Group – 16
Preparation, properties, structures and uses of ozone; Allotropic forms of sulphur; Preparation, properties, structures and uses of sulphuric acid (including its industrial preparation); Structures of oxoacids of sulphur.
Group – 17
Preparation, properties and uses of hydrochloric acid; Trends in the acidic nature of hydrogen halides;
Structures of Interhalogen compounds and oxides and oxoacids of halogens.
Group –18
Occurrence and uses of noble gases; Structures of fluorides and oxides of xenon.
16. d – and f – Block Elements Transition Elements
General introduction, electronic configuration, occurrence and characteristics, general trends in
properties of the first row transition elements - physical properties, ionizationenthalpy, oxidation states, atomic radii, colour, catalytic behaviour, magnetic properties, complex formation, interstitial compounds, alloy formation; Preparation, properties and uses of K2Cr 2O7 and KmnO4.
Inner Transition Elements
Lanthanoids - Electronic configuration, oxidation states and lanthanoid contraction.Actinoids - Electronic configuration and oxidation states.
17 Co-Ordination Compounds
Introduction to co-ordination compounds, Werner’s theory; ligands, coordination number, denticity,
chelation; IUPAC nomenclature of mononuclear coordination compounds, isomerism; Bonding-Valence bond approach and basic ideas of Crystal field theory, colour and magnetic properties; Importance of coordination compounds (in qualitative analysis, extraction of metals and in biological systems).
18 Environmental Chemistry
Environmental pollution - Atmospheric, water and soil.
Atmospheric pollution - Tropospheric and Stratospheric Tropospheric pollutants – Gaseous pollutants: Oxides of carbon, nitrogen and sulphur, hydrocarbons; their sources, harmful effects and prevention; Green house effect and Global warming; Acid rain;
Particulate pollutants: Smoke, dust, smog, fumes, mist; their sources, harmful effects and prevention.
Stratospheric pollution- Formation and breakdown of ozone, depletion of ozone layer - its mechanism and effects.
Water Pollution - Major pollutants such as, pathogens, organic wastes and chemical pollutants; their harmful effects and prevention.
Soil pollution - Major pollutants such as: Pesticides (insecticides,herbicides and fungicides), their harmful effects and prevention. Strategies to control environmental pollution.
Section-C: Organic Chemistry
19 Purification And Characterisation Of Organic Compounds
Purification - Crystallization, sublimation, distillation, differential extraction and chromatography - principles and their applications.
Qualitative analysis - Detection of nitrogen, sulphur, phosphorus and halogens.
Quantitative analysis (basic principles only) - Estimation of carbon, hydrogen, nitrogen, halogens,
sulphur, phosphorus. Calculations of empirical formulae and molecular formulae; Numerical problems in organic quantitative analysis.
20 Some Basic Principles Of Organic Chemistry
Tetravalency of carbon; Shapes of simple molecules - hybridization (s and p); Classification of organic compounds based on functional groups: - C = C - , - C h C – and those containing halogens, oxygen, nitrogen and sulphur; Homologous series; Isomerism - structural and stereoisomerism.
Nomenclature (Trivial and IUPAC) Covalent bond fission - Homolytic and heterolytic: free radicals,
carbocations and carbanions; stability of carbocations and free radicals, electrophiles and nucleophiles.
Electronic displacement in a covalent bond - Inductive effect, electromeric effect, resonance and
hyperconjugation
21 Hydrocarbons
Classification, isomerism, IUPAC nomenclature, general
methods of preparation, properties and reactions.
Alkanes - Conformations: Sawhorse and Newman
projections (of ethane); Mechanism of halogenation of
alkanes.
Alkenes - Geometrical isomerism; Mechanism of
electrophilic addition: addition of hydrogen, halogens,
water, hydrogen halides (Markownikoff’s and peroxide
effect); Ozonolysis and polymerization.
Alkynes - Acidic character; Addition of hydrogen,
halogens, water and hydrogen halides; Polymerization.
Aromatic hydrocarbons - Nomenclature, benzene -
structure and aromaticity; Mechanism of electrophilic
substitution: halogenation, nitration, Friedel – Craft’s
alkylation and acylation, directive influence of functional
group in mono-substituted benzene
22 Organic Compounds Containing Halogens
General methods of preparation, properties and
reactions; Nature of C-X bond; Mechanisms of
substitution reactions.Uses; Environmental effects of
chloroform & iodoform.
23 Organic Compounds Containing Oxygen
General methods of preparation, properties, reactions
and uses.
Alcohols, Phenols And Ethers Alcohols: Identification
of primary, secondary and
tertiary alcohols; mechanism of dehydration.
Phenols: Acidic nature, electrophilic substitution
reactions: halogenation, nitration and sulphonation,
Reimer - Tiemann reaction.Ethers: Structure.
Aldehyde and Ketones: Nature of carbonyl
group;Nucleophilic addition to >C=O group, relative
reactivities of aldehydes and ketones; Important
reactions such as – Nucleophilic addition reactions
(addition of HCN, NH3 and its derivatives), Grignard
reagent; oxidation; reduction (Wolff Kishner and
Clemmensen); acidity of - hydrogen, aldol condensation,
Cannizzaro reaction, Haloform reaction; Chemical tests
to distinguish between aldehydes and Ketones.
Carboxylic Acids Acidic strength and factors affecting it
24 Organic Compounds Containing Nitrogen
General methods of preparation, properties, reactions
and uses. Amines: Nomenclature, classification,
structure, basic character and identification of primary,
secondary and tertiary amines and their basic character.
Diazonium Salts: Importance in synthetic organic
chemistry.
25 Polymers General introduction and classification of polymers,
general methods of polymerizationaddition
and condensation, copolymerization; Natural and
synthetic rubber and vulcanization; some important
polymers with emphasis on their monomers and uses -
polythene, nylon, polyester and bakelite.
26 Biomolecules
General introduction and importance of biomolecules.
Carbohydrates - Classification: aldoses and ketoses;
monosaccharides (glucose and fructose) and constituent
monosaccharides of oligosacchorides (sucrose, lactose
and maltose).
Proteins - Elementary Idea of - amino acids, peptide
bond, polypeptides; Proteins: primary, secondary,
tertiary and quaternary structure (qualitative idea only),
denaturation of proteins, enzymes.
Vitamins - Classification and functions.
Nucleic Acids - Chemical constitution of DNA and RNA.
Biological functions of nucleic
acids.
27 Chemistry
In Everyday Life Chemicals in medicines - Analgesics, tranquilizers,
antiseptics, disinfectants, antimicrobials, antifertility
drugs, antibiotics, antacids, antihistamins – their
meaning and common examples.Chemicals in food - Preservatives, artificial sweetening
agents - common examples.
Cleansing agents - Soaps and detergents, cleansing
action
28 Principles Related To Practical Chemistry
• Detection of extra elements (N,S, halogens) in organic
compounds; Detection of the following functional groups:
hydroxyl (alcoholic and phenolic), carbonyl (aldehyde
and ketone), carboxyl and amino groups in organic
compounds.
• Chemistry involved in the preparation of the following:
Inorganic compounds: Mohr’s salt, potash alum. Organic
compounds: Acetanilide, pnitroacetanilide, aniline
yellow, iodoform.
• Chemistry involved in the titrimetric excercises - Acids
bases and the use of indicators, oxalic-acid vs KMnO4,
Mohr’s salt vs KMnO4
• Chemical principles involved in the qualitative salt
analysis:
· Cations - Pb2+ , Cu2+, AI3+, Fe3+, Zn2+, Ni2+, Ca2+,
Ba2+, Mg2+, NH4+.
· Anions- CO3 2-, S2-, SO4 2-, NO2-, NO3-, CI -, Br, I.
· (Insoluble salts excluded).
• Chemical principles involved in the following
experiments:
1. Enthalpy of solution of CuSO4
2. Enthalpy of neutralization of strong acid and strong
base.
3. Preparation of lyophilic and lyophobic sols.
4. 4. Kinetic study of reaction of iodide ion with hydrogen
peroxide at room temperature.
Wednesday, December 17, 2014
JEE Revision - Atomic structure - Basics
Thomson Model
J.J. Thomson studied the properties of cathode rays. Cathode rays were observed in tubes with gas at low pressures when electric charge was applied. The gas starts conducting electricity at low pressure and rays appear. During these studies, Thomson discovered electrons in 1897.
The experiments led to the conclusion that the particles comprising cathode rays were the same irrespective of the material of the cathode and the gas used in discarge tubes, The particles had the same mass and charge. Hence it was concluded that electrons are universal constituents of all matter.
Subsequently proton was also discovered. Rutherford's name can be mentioned in the case of proton as an important researcher.
Thomson proposed that the positive charge is spread over a sphere in which the electrons are embedded. This make the atom neutral. The model was also called Thomson's plum pudding model.
Rutherford model
In 1913, Niels Bohr proposed a model of the atom. He proposed that the electrons in an atom could only be in certain orbits, or energy levels, around the nucleus. Refinement of Bohr theory led to the modern theory of atomic structure based on quantum mechanics.
Wave mechanical model
J.J. Thomson studied the properties of cathode rays. Cathode rays were observed in tubes with gas at low pressures when electric charge was applied. The gas starts conducting electricity at low pressure and rays appear. During these studies, Thomson discovered electrons in 1897.
The experiments led to the conclusion that the particles comprising cathode rays were the same irrespective of the material of the cathode and the gas used in discarge tubes, The particles had the same mass and charge. Hence it was concluded that electrons are universal constituents of all matter.
Subsequently proton was also discovered. Rutherford's name can be mentioned in the case of proton as an important researcher.
Thomson proposed that the positive charge is spread over a sphere in which the electrons are embedded. This make the atom neutral. The model was also called Thomson's plum pudding model.
Rutherford model
In 1913, Niels Bohr proposed a model of the atom. He proposed that the electrons in an atom could only be in certain orbits, or energy levels, around the nucleus. Refinement of Bohr theory led to the modern theory of atomic structure based on quantum mechanics.
Wave mechanical model
Saturday, March 22, 2014
Magnesium - Chemistry
Magnesium occupies sixth position in order of the abundance on earth.
Magnesium is greyish white metal.
Magnesium is the lightest metal used in industry and it has a density less than two thirds of aluminium. Magnesium is an important alloying metal.
Uses:
Some of the alloys of magnesium containing more than 90% magnesium and 2 to 9% of Aluminium and 1% zinc are used in automobile engines, in aircrafts and in making balances.
Up to 5% magnesium is added to most commercial aluminium alloys (duralumin, magnalium) to improve its resistance to corrosion, mechanical properties and weldability.
Magnesium is used as a reducing agent in metallurgy for the production of metals such as Titanium (Ti), Zirconium (Zr) and Hf.
Magnesium power is used in fireworks.
It is part of alkyl magnesium halide (RMgX), the Grignard reagent and it is useful for making number of organic compounds.
Magnesium hydroxide and magnesium carbonate are used in making toothpastes.
Magnesium hydroxide (milk of magnesia) is used as an antacid. It neutralises excess of acid in stomach and thus it is used as medicine.
Ores of Magnesium
1. Carnallite
2. Magnesite
3. Dolomite
4. Epsom salt or epsomite
5. Langbeinite
6. Asbestos
Extraction of Magnesium from Its Ores
Magnesium is finally extracted by the electrolysis of its molten anhydrous salts.
From Magnesite
The ore MgCO3 is calcined to form the oxide MgO.
The oxide is mixed with carbon and heated in a current of Cl2 gas to form magnesium chloride.
Magnesium chloride is subjected to electrolysis.
Electrolysis of Magnesium chloride
Magnesium chloride is with a mixture of sodium chloride and calcium chloride and heated to 973 K - 1023 K. The mixture melts at this temperature and the electrolysis in carried out in an iron vessel which serves as the cathode. A graphite rod serves as anode. During the electrolysis an inert gas such as coal gas is passed through the cell to check the oxidation of magnesium. At cathode magnesium will emerge in molten state and at anode chlorine gas will be released. The liquid magnesium (m.p. 924K) is removed from time to time from the top of the vessel.
Magnesium is a s-Block element.
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