CHEMISTRY – STRUCTURE OF ATOM
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1. Introduction
Structure of atom explains how subatomic particles are arranged inside an atom. This chapter is
the base of modern chemistry and quantum mechanics.
2. Discovery of Subatomic Particles
1 Electron – Discovered by J.J. Thomson (Cathode Ray Experiment)
2 Proton – Discovered by Goldstein
3 Neutron – Discovered by James Chadwick
3. Atomic Models
1 Thomson Model – Atom is a positively charged sphere with electrons embedded
2 Rutherford Model – Dense nucleus with electrons revolving around it
3 Bohr Model – Electrons revolve in fixed energy levels
4. Bohr’s Model – Important Formulae
1 Energy of electron: En = −13.6 / n² eV
2 Radius of orbit: rn = 0.529 × n² / Z Å
3 Velocity of electron: vn = 2.18 × 10■ × Z / n m/s
5. Dual Nature of Matter
Particles show both wave and particle nature. de Broglie wavelength λ = h / mv
6. Heisenberg Uncertainty Principle
It is impossible to determine exact position and momentum of an electron simultaneously. ∆x ×
∆p ≥ h / 4π
7. Quantum Mechanical Model
Electrons do not move in fixed orbits but exist in orbitals described by wave functions. Probability
of finding an electron is given by ψ².
8. Quantum Numbers
Quantum Number Symbol Meaning
Principal n Energy level
Azimuthal l Shape of orbital
Magnetic m Orientation
Spin s Spin of electron
9. Shapes of Orbitals
■ Ultimate Premium Notes (Boards + JEE + NEET – Full Coverage)
1. Introduction
Structure of atom explains how subatomic particles are arranged inside an atom. This chapter is
the base of modern chemistry and quantum mechanics.
2. Discovery of Subatomic Particles
1 Electron – Discovered by J.J. Thomson (Cathode Ray Experiment)
2 Proton – Discovered by Goldstein
3 Neutron – Discovered by James Chadwick
3. Atomic Models
1 Thomson Model – Atom is a positively charged sphere with electrons embedded
2 Rutherford Model – Dense nucleus with electrons revolving around it
3 Bohr Model – Electrons revolve in fixed energy levels
4. Bohr’s Model – Important Formulae
1 Energy of electron: En = −13.6 / n² eV
2 Radius of orbit: rn = 0.529 × n² / Z Å
3 Velocity of electron: vn = 2.18 × 10■ × Z / n m/s
5. Dual Nature of Matter
Particles show both wave and particle nature. de Broglie wavelength λ = h / mv
6. Heisenberg Uncertainty Principle
It is impossible to determine exact position and momentum of an electron simultaneously. ∆x ×
∆p ≥ h / 4π
7. Quantum Mechanical Model
Electrons do not move in fixed orbits but exist in orbitals described by wave functions. Probability
of finding an electron is given by ψ².
8. Quantum Numbers
Quantum Number Symbol Meaning
Principal n Energy level
Azimuthal l Shape of orbital
Magnetic m Orientation
Spin s Spin of electron
9. Shapes of Orbitals
