Question

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

• A. 5
• B. 6
• C. 7
• D. 4

Answer 1

The correct option is A 5

The number of electrons in the shell is given as 2 in K shell, 8 in L shell and 5 in the M shell.

Thus, the atom has in total of 2+8+5 = 15 electrons.

The element is phosphorus.

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

The valence shell is shell 3 i.e. M shell and it has $3s^{2}3p^3$ electrons.

The atom has a total $5$ electrons in M shell.

Hence, option $\left(A\right)$ is correct.