Bohr's Model Postulates for NEET: Key Points, Tricks & MCQs
Bohr's ModelStructure of AtomNEET ChemistryNEET 2025Bohr PostulatesAtomic Structure
Bohr's Model Postulates for NEET: Key Points, Tricks & MCQs
Structure of Atom·2 min read·NEET 2026
What NEET Asks
Direct conceptual questions on individual postulates of Bohr's model.
Application of angular momentum quantization formula for specific orbits.
Basis for explaining the stability of atoms and hydrogen spectral lines.
Key Points
Stationary States: Electrons revolve in fixed circular orbits (called stationary states) without radiating energy.
Quantized Angular Momentum: Only orbits where the angular momentum (mvr) is an integral multiple of h/2π are allowed (mvr = nh/2π, where n = 1, 2, 3...). Electrons cannot exist between these orbits.
Energy Transitions: Energy is emitted when an electron jumps from a higher to a lower energy state, and absorbed when it moves from a lower to a higher state. The energy difference (where ν is the frequency of radiation).
ΔE = E₂ - E₁ = hν
Centripetal Force: The electrostatic force of attraction between the nucleus and the electron provides the necessary centripetal force for the electron's motion (kZe²/r² = mv²/r).
Limitations: Bohr's model is strictly applicable only to single-electron species (e.g., H, He⁺, Li²⁺, Be³⁺).
Must-Know Formula / Reaction
mvr = nh/2π
m: mass of the electron
v: velocity of the electron
r: radius of the electron's orbit
n: principal quantum number (or orbit number, 1, 2, 3...)
h: Planck's constant
This formula represents the quantization of angular momentum, a fundamental postulate.
Common Mistakes
Students often apply Bohr's model concepts to multi-electron atoms, which is incorrect due to electron-electron repulsions.
Don't confuse 'stationary states' with electrons being static; they are in motion but not radiating energy.
Misinterpreting the negative sign in energy calculations; emission leads to a negative ΔE, but the energy of the emitted photon is a positive value.
Rapid Revision
Bohr's model postulates fixed, non-radiating orbits (stationary states) with quantized angular momentum (mvr = nh/2π). Energy changes only occur during transitions (ΔE = hν). It's valid solely for hydrogen and hydrogen-like species.
Frequently Asked Questions
What are the main postulates of Bohr's atomic model?▾
Bohr's model states that electrons revolve in specific, stable orbits without radiating energy. Their angular momentum is quantized (`mvr = nh/2π`), and energy is emitted or absorbed only during transitions between these orbits. The centripetal force for orbit is from electrostatic attraction.
Why is Bohr's model only applicable to hydrogen-like species?▾
Bohr's model simplifies the atom to a single electron orbiting a nucleus, calculating forces and energies based on this interaction alone. It fails to account for the complex inter-electron repulsions present in multi-electron atoms, making its predictions inaccurate for them.
What is meant by 'quantization of angular momentum' in Bohr's model?▾
It signifies that an electron can only revolve in orbits where its angular momentum (`mvr`) is an integral multiple of `h/2π`. This implies that only certain discrete orbits are allowed, and electrons cannot occupy positions or energy levels in between these defined orbits.
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