Question

Which of the following electron configuration is not possible for an atom?

1s2 2s2 2p6 3s2 3p6 4s2 3d1

1s2 2s2 2p6 2d5

1s2 2s2 2p6 3s1

1s2 2s2 2p1

Answer 1

Answer:

1s2 2s2 2p6 2d5

Explanation:

The number of possible subshells in the $nth$ shell is equal to $n$. Therefore, 2d subshell does not exist.

Source:

Kotz, J., Treichel, P., Townsend, J. and Treichel, D., 2018. Chemistry & chemical reactivity. 10th ed. Cengage Learning.