What is the ground state electron configuration of oxygen?

Oxygen's ground state is ##1s^(2)2s^(2)2p^(4)##.

Oxygen has 8, so it has 8 electrons. Each "s" subshell can only hold 2 electrons before it begins to fill a "p" subshell.

Remember that the first energy level only contains a single "s" subshell, which means that there is no such thing as a "1p" subshell.

You can use the following diagram to show you the order of filling orbitals.

The diagram shows that you fill the##1s##, then the ##2s##, then the ##2p## and so on until you have added enough electrons.

Therefore, you add 2 electrons to the ##1s## and two electrons to the ##2s##. That leaves 4 electrons to go into the ##2p## level.

The electron configuration of O is ##1s^2 2s^2 2p^4##.