Fitting electrons into orbitals

Because for the moment we are only interested in the electronic structures of hydrogen and carbon, we don't need to concern ourselves with what happens beyond the second energy level.

Remember:

At the first level there is only one orbital - the 1s orbital.

At the second level there are four orbitals - the 2s, 2p_x, 2p_yand 2p_z orbitals.

Each orbital can hold either 1 or 2 electrons, but no more.