Question

The quantum numbers n = 4, l = 1, m_l = 0 could represent a valence electron in which atom in its ground state?

Answer choices are Fe, In, Pd, and Se, and answer key says it is Se.
I know that these quantum numbers refer to 4s electrons, so I eliminated B and C. How can I tell if the answer is Fe or Se, since both seem to have 4s electrons?
Thanks!

Answer 1

`l = 1` doesn’t represent s orbital. Given quantum numbers refers to either `4p^2` electron or `4p^5` electron.

Explanation:

`n = 4` represents that atom is in 4th period. So, answer is either Fe or Se

`l = 1` represents p orbital.

In p-block elements, the last (valence) electron enters in the outermost p-orbital. Therefore, atom belongs to p-block.

• Fe is d-block element
• Se is p-block element

Se is the correct answer.