Atomic Structure — Question 3

Drawbacks of Rutherford's Atomic Model :

• In Rutherford's model of the atom - the electrons revolve around the nucleus and the attractive force of the positively charged nucleus would be balanced by the centrifugal force arising due to the rotation of electron.
• If an electron moves round the nucleus - it must radiate out energy and gradually move towards the nucleus following a spiral path - till it collides and ultimately collapses in it.
• Thus, Rutherford's model could not explain correctly the stability of an atom.

Postulates of Bohr's Atomic Model :

• Electrons revolve around the nucleus in fixed orbits or energy levels, possessing certain amount of energy.
• The integer n represents the various energy levels 1, 2, 3 or K, L, M starting from the innermost.
• As long as the electrons rotates in one of the energy levels - it neither loses or absorbs energy. When energy is supplied initially to the atoms - an electron moves to an orbit of higher energy. When this electron drops back to the original orbit - energy is radiated by the atom - according to equation E₂ - E₁ = hγ

[E₂ and E₁ are energy states of the electron in higher and lower orbit.]

Bohr's model gave the preciseness of location and mode of rotation of electron around the nucleus.