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Atomic Structure
Bohr model, quantum numbers, electronic configuration
Key Concepts
- Bohr model: electrons in circular orbits; quantised energy and angular momentum
- Quantum numbers: n (principal), l (azimuthal), m_l (magnetic), m_s (spin)
- Aufbau principle: fill lowest energy orbitals first
- Hund's rule: maximum unpaired electrons in degenerate orbitals
- Pauli exclusion principle: no two electrons can have identical quantum numbers
Important Formulae
| Bohr energy (hydrogen) | E_n = −13.6/n² eV |
| de Broglie wavelength | λ = h/mv |
| Heisenberg uncertainty | Δx · Δp ≥ h/4π |
| Orbital angular momentum | L = √[l(l+1)] · h/2π |
| Max electrons in shell n | 2n² |
Quick Tips
- l ranges from 0 to n−1; m_l ranges from −l to +l; m_s = +½ or −½.
- Order of filling: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p … (n+l rule).
- Cr is [Ar]3d⁵4s¹ and Cu is [Ar]3d¹⁰4s¹ — exceptions due to extra stability of half-filled/fully-filled d-orbitals.
Practice Questions
Practice 20 randomly selected NEET questions on Atomic Structure. Answers are revealed after each question.
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