Question

A neutral atom of an element has 2K, 8L and 5M electrons. What is the number of unpaired electrons?

• A. 2
• B. 3
• C. 4
• D. 5

Answer 1

Answer: (B)

3

The number of electrons in the shells are given as 2, 8, and 5. Thus, the atom has in total 15 electrons. This means that the atom is phosphorous.

The electronic configuration will be as follows.

The electronic configuration of P will be : $1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

Number of unpaired electrons in this atom are 3.