Question

Question 41
What are the postulates of Bohr's model of an atom?

Answer 1

The postulates of Bohr's model of an atom are as follows:
(i) In an atom, the electrons revolve around the nucleus in certain definite circular paths called orbits or shells. These are represented by the letters K, L. M, N $\dots$ or the numbers n = 1, 2, 3, 4 $\dots$

(ii) The maximum number of electrons present in a shell is given by the formula $2n^2$, where n is the orbit number or energy level index, 1, 2, 3 $\dots$ Hence, the maximum number of electrons in different shells are as follows.
First orbit (K shell) will be $=2\times 1^2=2$,
Second orbit (M shell) will be $=2\times 2^2=8$
Third orbit (M shell) will be $=2\times 3^2=18$ and so on.

(iii) The maximum number of electrons that can be accommodated in the outermost orbit is 8.

(iv) Electrons are not accommodated in a given shell unless the inner shells are filled. That is the shells are filled in a step-wise manner.

(v) While revolving in discrete orbits the electrons do not radiate energy.