Question

(1) As long as an electron revolves in a particular orbit, the electron does not lose its energy. Therefore, these orbits are called stationary orbits and the electrons are said to be in stationary energy states
(2) Each orbit or shell is associated with a definite amount of energy. Hence, these are also called energy levels
(3) An electron jumps from a lower energy level to a higher energy level, by absorbing energy. It jumps from a higher energy level to a lower energy level by emitting energy in the form of electromagnetic radiation
(4) Electrons move around the nucleus in specified circular paths called orbits or shells or energy levels and are designated as K, L, M and N shells respectively

Arrange the above postulates of Bohr's theory in a correct sequence.

• A. $4,1,3,2$
• B. $4,2,1,3$
• C. $4,1,2,3$
• D. $2,4,1,3$

Answer 1

The correct option is B

$4,2,1,3$

The explanation for the correct option: (B)

The postulates of Bohr's theory in the correct sequence are:

1. Electrons move around the nucleus in specified circular paths called orbits or shells or energy levels and are designated as K, L. M, and N shells, respectively.
2. Each orbit or shell is associated with a definite amount of energy. Hence, these are also called energy levels.
3. As long as the electron revolves in a particular orbit, the electron does not lose its energy. Therefore, these orbits are called stationary orbits, and the electrons are said to be in stationary energy states.
4. An electron jumps from a lower to a higher energy level by absorbing energy. It jumps from a higher to a lower energy level by emitting energy in the form of electromagnetic radiation.
5. Hence, the correct sequence is $4,2,1,3$.

The explanation for the incorrect options:

(A) The postulates of Bohr's theory in a correct sequence are not $4,1,3,2$.

(C) The given order $4,1,2,3$ is not the correct sequence of the postulates of Bohr's theory.

(D) The postulates of Bohr's theory in a correct sequence are not $2,4,1,3$.

Hence, option (B) is correct - The postulates of Bohr's theory in a correct sequence are $4,2,1,3$.