Bohr’s Atomic Model

Introduction:

Neil Bohr was a Danish physicist who joined Rutherford in 1912 for his post-doctoral research. He presented his model of the atom in 1913. He also explained the line spectrum of the hydrogen atom.

Main postulates of Bohr:

Bohr’s atomic model was based on the following postulates:

The hydrogen atom consists of a tiny nucleus and electrons are revolving in one of the circular orbits of radius ‘r’ around the nucleus.
Each orbit has a fixed energy that is quantized.
As long as an electron remains in a particular orbit, it does not radiate or absorb energy in the form of photons. The energy is emitted or absorbed only when an electron jumps from one orbit to another.
When an electron jumps from a lower orbit to a higher orbit, it absorbs energy and when it jumps from a higher orbit to a lower orbit it radiates energy. This change in energy, E is given by following Planck’s equation: ∆E = E₂ – E₁ = hv.

Where, ‘h’ is Planck’s constant equal to 6.63 x 10^-34 J.s, and ‘v’ is the frequency of light. Electrons can revolve only in orbits of a fixed angular moment (mvr).

Limitations of Bohr’s atomic model:

Bohr’s model failed to explain the following:

Zeeman effect.
Stark effect.
Heisenberg’s uncertainty principle.
Spectra of large atoms.
Polyelectronic species like Li,Be, He atoms.

Bohr’s Atomic Model

Bohr’s Atomic Model

Introduction:

Main postulates of Bohr:

Limitations of Bohr’s atomic model:

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