Importance of Core Revision Points: Core Revision Points are important because if you remember them strongly, many more points related to them will come out of your memory and help you to answer question and problems. Read them many times and make sure you remember them very strongly.
JEE Syllabus
Atomic structure
Bohr model, spectrum of hydrogen atom, quantum numbers;
Wave-particle duality, de Broglie hypothesis;
Uncertainty principle;
Quantum mechanical picture of hydrogen atom (qualitative treatment), shapes of s, p and d orbitals;
Electronic configurations of elements (up to atomic number 36);
Aufbau principle;
Pauli's exclusion principle and Hund's rule;
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Electron was discovered by J.J. Thomson at the end of 19th century.
An electron may be defined as a sub-atomic particle which carries one unit negative charge (1.602*10^-19c) and has a mass (9.1*10^-31 kg) equal to 1/1837th of that of hydrogen atom.
Proton is a sub-atomic particle which carries one unit positive charge (1.602*10^19 coulombs) and has mass (1.67*10^-27 kg) which is equal to that of an atom of hydrogen.
3.2 arranging electrons and protons in an atom
3.3 Rutherford's Scattering Experiment
3.4 Concept of Atomic Number and Discovery of Neutron
1. Dual behaviour of the electromagnetic radiation.
2. Atomic spectra
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.
1. Wave length
2. Frequency
3. Velocity
4. Amplitude
Electromagnetic spectrum
3.7 Particle Nature of Electromagnetic Radiation and Planck's Quantum Theory
Emission spectra
Absorption spectra
Emission spectrum from Hydrogen atom
3.9 Failure of Rutherford Model
Bohr's model of the atom
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.
Bohr's model is based on particle theory.
As wave-particle duality which says that all micromatter particle exhibit duality a new model is proposed.
Debroglie p = h/λ
3.12 Wave Mechanical Model of Atom
Uncertainty principle Δp* Δx ≥h/4π
3.13 Quantum Numbers
The quantum mechanics model
Principal quantum number-Shell,Azimuthal quantum number-sublevel,Magnetic quantum number-orbital, spin quantum number
The orbits are called as shells. The energy level of orbits or shells increases as they increase in distance from the nucleus of the atom. The orbits or shells are represented by numbers as 1,2,3,4,5,6 or 7. They are represented by letters as K,L,M,N,O,P,Q.
Sublevel of an Orbit
The energy levels, or orbits or shells are further divided into sublevels, or subshells. These subshells are designated by letters: s for the first possible sublevel, p for the second possible sublevel, d for the third, f for the fourth, g for the fifth, and from here on they simply go in alphabets.
The number of sublevels of each energy level is equal to the number of the energy levels. This means energy level 1, the K shell will have only one sub levels – s sublevel. The energy level 2, the L shell will have 2 sub levels – s and p.
Orbitals
Sublevels have further divisions called orbitals. Electrons are found in these orbitals. Each orbital contains two electrons.
“s” sublevel has only one orbital. “p” sublevel has 3 orbitals. “d” sublevel has 5 orbitals. “f” sublevel has 7 orbitals.
The two electons in each orbital spin in different directions.
3.14 Pauli's Exclusion Principles
Pauli's exclusion principle: No two electrons can have all four same quantum numbers
3.15 Shapes of Orbitals
Shape of Orbitals
1. Spherical shape for s.
2. Dumbbell shape for orbitals of p.
3. Four-lobed shape for orbitals of d.
4. Complex shape for all orbitals of higher sublevels.
3.16 Energy Level Diagram for Electrons in an Atom
3.17 Electron Configurations of Atoms
Electrons occupy the lowest energy sublevels that are available. This is known as ‘aufbau’ order or principles.
Hund’s rule says that, for any set of orbitals of equal energy say p orbitals of orbit 2, there is one electron is each orbital before the second electron enters or occupies an orbital.
The energy level of some sublevels at higher orbits is less than the some sublevels at lower orbitals. This fact is to be kept in mind when electron configuration is determined for any atom. The increasing order of energy levels of sublevels is:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f*, 5d, 6p, 7s, 5f*, 6d, 7p, 8s
Jauhar Chapter Contents
3.1 Fundamental Particles
3.2 arranging electrons and protons in an atom
3.3 Rutherford's Scattering Experiment
3.4 Concept of Atomic Number
3.5 Developments Leading to the Bohr Model of Atom
3.6 Nature of Light and Electromagnetic Radiation
Particle Nature of Electromagnetic Radiation and Planck's Quantum Theory
3.8 Atomic Spectra
3.9 Failure of Rutherford Model
3.10 Concepts of Energy Levels or Orbits
3.11 Modern Concept of Structure of Atom
3.12 Wave Mechanical Model of Atom
3.13 Quantum Numbers
3.14 Pauli's Exclusion Principles
3.15 Shapes of Orbitals
3.16 Energy Level Diagram for Electrons in an Atom
3.17 Electron Configurations of Atoms
Updated 8 January 2020, 21 May 2015
Published first 19 January 2008
JEE Syllabus
Atomic structure
Bohr model, spectrum of hydrogen atom, quantum numbers;
Wave-particle duality, de Broglie hypothesis;
Uncertainty principle;
Quantum mechanical picture of hydrogen atom (qualitative treatment), shapes of s, p and d orbitals;
Electronic configurations of elements (up to atomic number 36);
Aufbau principle;
Pauli's exclusion principle and Hund's rule;
----------------
3.1 Fundamental Particles
Electron was discovered by J.J. Thomson at the end of 19th century.
An electron may be defined as a sub-atomic particle which carries one unit negative charge (1.602*10^-19c) and has a mass (9.1*10^-31 kg) equal to 1/1837th of that of hydrogen atom.
Proton is a sub-atomic particle which carries one unit positive charge (1.602*10^19 coulombs) and has mass (1.67*10^-27 kg) which is equal to that of an atom of hydrogen.
3.2 arranging electrons and protons in an atom
3.3 Rutherford's Scattering Experiment
3.4 Concept of Atomic Number and Discovery of Neutron
3.5 Developments Leading to the Bohr Model of Atom
1. Dual behaviour of the electromagnetic radiation.
2. Atomic spectra
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.
3.6 Nature of Light and Electromagnetic Radiation
Characteristics of wave motion1. Wave length
2. Frequency
3. Velocity
4. Amplitude
Electromagnetic spectrum
3.7 Particle Nature of Electromagnetic Radiation and Planck's Quantum Theory
3.8 Atomic Spectra
Emission spectra
Absorption spectra
Emission spectrum from Hydrogen atom
3.9 Failure of Rutherford Model
3.10 Concepts of Energy Levels or Orbits
Bohr's model of the atom
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.
Bohr's model is based on particle theory.
3.11 Modern Concept of Structure of Atom
As wave-particle duality which says that all micromatter particle exhibit duality a new model is proposed.
Debroglie p = h/λ
3.12 Wave Mechanical Model of Atom
Uncertainty principle Δp* Δx ≥h/4π
3.13 Quantum Numbers
The quantum mechanics model
Principal quantum number-Shell,Azimuthal quantum number-sublevel,Magnetic quantum number-orbital, spin quantum number
The orbits are called as shells. The energy level of orbits or shells increases as they increase in distance from the nucleus of the atom. The orbits or shells are represented by numbers as 1,2,3,4,5,6 or 7. They are represented by letters as K,L,M,N,O,P,Q.
Sublevel of an Orbit
The energy levels, or orbits or shells are further divided into sublevels, or subshells. These subshells are designated by letters: s for the first possible sublevel, p for the second possible sublevel, d for the third, f for the fourth, g for the fifth, and from here on they simply go in alphabets.
The number of sublevels of each energy level is equal to the number of the energy levels. This means energy level 1, the K shell will have only one sub levels – s sublevel. The energy level 2, the L shell will have 2 sub levels – s and p.
Orbitals
Sublevels have further divisions called orbitals. Electrons are found in these orbitals. Each orbital contains two electrons.
“s” sublevel has only one orbital. “p” sublevel has 3 orbitals. “d” sublevel has 5 orbitals. “f” sublevel has 7 orbitals.
The two electons in each orbital spin in different directions.
3.14 Pauli's Exclusion Principles
Pauli's exclusion principle: No two electrons can have all four same quantum numbers
3.15 Shapes of Orbitals
Shape of Orbitals
1. Spherical shape for s.
2. Dumbbell shape for orbitals of p.
3. Four-lobed shape for orbitals of d.
4. Complex shape for all orbitals of higher sublevels.
3.16 Energy Level Diagram for Electrons in an Atom
3.17 Electron Configurations of Atoms
Electrons occupy the lowest energy sublevels that are available. This is known as ‘aufbau’ order or principles.
Hund’s rule says that, for any set of orbitals of equal energy say p orbitals of orbit 2, there is one electron is each orbital before the second electron enters or occupies an orbital.
The energy level of some sublevels at higher orbits is less than the some sublevels at lower orbitals. This fact is to be kept in mind when electron configuration is determined for any atom. The increasing order of energy levels of sublevels is:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f*, 5d, 6p, 7s, 5f*, 6d, 7p, 8s
Jauhar Chapter Contents
3.1 Fundamental Particles
3.2 arranging electrons and protons in an atom
3.3 Rutherford's Scattering Experiment
3.4 Concept of Atomic Number
3.5 Developments Leading to the Bohr Model of Atom
3.6 Nature of Light and Electromagnetic Radiation
Particle Nature of Electromagnetic Radiation and Planck's Quantum Theory
3.8 Atomic Spectra
3.9 Failure of Rutherford Model
3.10 Concepts of Energy Levels or Orbits
3.11 Modern Concept of Structure of Atom
3.12 Wave Mechanical Model of Atom
3.13 Quantum Numbers
3.14 Pauli's Exclusion Principles
3.15 Shapes of Orbitals
3.16 Energy Level Diagram for Electrons in an Atom
3.17 Electron Configurations of Atoms
Updated 8 January 2020, 21 May 2015
Published first 19 January 2008
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The post will be updated in June 2015
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