## Thursday, May 21, 2015

### IIT JEE Ch.3. ATOMIC STRUCTURE Core Points for Revision

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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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
3.7 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

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 dualitya new model is proposed.

Debroglie p = h/λ

Uncertainty principle Δp* Δx ≥h/4π

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.

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

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

Updated 21 May 2015
Published first 19 January 2008

#### 2 comments:

KVSSNrao said...

I remember my daughter Dedeepya today 21 May 2015.

KVSSNrao said...

The post will be updated in June 2015