Question

How many electrons can be in each orbital?

Answer 1

Only 2 electrons per orbital.

Explanation:

Paule's exclusion principle states that no two electrons can have the exact energy levels and configuration.

So an orbital can hold only two electrons. One electron with a clockwise spin and one electron with a counter clockwise spin.
This follows the exclusion principle because the electrons are different in spin. A third electron that tried to enter the orbital would be repelled by the electron that had the same spin.

This does not exclude the possibility that an orbital might hold only one electron.

Any given orbital can hold either one or two electrons.