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.
Sample Practice Questions
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Rutherford's gold foil experiment showed that:
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Answer: The nucleus is small, dense and positively charged
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The maximum number of orbitals in n=3 shell:
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Answer: 9
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The electron having highest energy in ²³Na (sodium):
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Answer: 3s¹
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The shape of a p orbital is:
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Answer: Dumbbell
Practice Questions
Practice 20 randomly selected NEET questions on Atomic Structure. Answers are revealed after each question.
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What are the key concepts in Atomic Structure for NEET?
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.
Which formulae are important for Atomic Structure in NEET?
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.
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