The orbital diagram shows the valence electrons of sulfur, which has 16 electrons. If the electrons were added to the atom one at a time, which would be the last electron to occupy an orbital?

3px

Explanation:

The electronic configuration of sulphur is given as;

1s2 2s2 2p6 3s2 3px2 3py1 3pz1.

Recall that in accordance with Hund's rule, electrons occur singly first before pairing takes place during the filling of degenerate orbitals.

The last sub-level into which electrons are filled in sulphur is the 3p sub-level having three degenerate orbitals, 3px, 3py and 3pz.

According to Hund's rule, these levels are first singly filled before pairing begins. Hence the last electron in sulphur goes into the 3px orbital.