3. Bohr_s Model of Hydrogen Atom

Bohr’s Model of Hydrogen Atom

Bohr suggested a new model for the atom as Rutherford’s atom model was unstable. He introduced the concept of stationary orbits.

Postulates of Bohr’s Atom Model

• In a hydrogen atom, the negatively charged electron revolves in a circular orbit around the heavy positively charged nucleus. These are the stationary (orbits) states of the atom.
• The electrons revolve around the nucleus only in those orbits for which the angular momentum is the integral multiple of

• Electron might make a transition from one of its specified non-radiating orbits to another of lower energy. When it does so, a photon is emitted having energy equal to the energy difference between the initial and final state.

hν = E_i − E_f

E_i > E_f,

Angular momentum is given by,

L = mvr

According to Bohr’s 2^nd postulate,

n → Principle quantum

v_n → Speed of moving electron in the n^th orbit

r_n→ Radius of n^thorbit

For n = 1 (innermost orbit),

This is called Bohr radius, represented by the symbol a₀.

Total energy,

Energy level diagram for a hydrogen atom: