Question

What is the second quantum number of a `1s^2` electron in phosphorus `1s^2 2s^2 2p^6 3s^2 3p^3`?

Answer 1

`l=0`

Explanation:

As you know, four quantum numbers are used to describe the position and spin of an electron in an atom.

In your case, you want to know the value of the angular momentum quantum number, `l`, for an electron located in the 1s-orbital.

As you can see, the angular momentum quantum number depends on the value of the principal quantum number, `n`, which tells you the energy level on which the electron is found.

The 1s-orbital is located on the first energy level, hence the number `1` used in its name.

Since

`l = 0, 1, 2, ..., (n-1)" "` and `" "n = 1`

you will have only one possible value for `l`, and that is `l=0`.

An s-orbital will always have `l=0`, regardless of energy level.