How many electrons are present in a 4p orbital?

A `4p` orbital, which is part of the `p` subshell located on the fourth energy level, can hold a maximum of two electrons.

In fact, any orbital, regardless of its energy level, subshell, and orientation, can hold a maximum of two electrons, one having spin-up and one having spin-down.

This is the case because according to the Pauli Exclusion Principle, two electrons located in an atom cannot share a complete set of four quantum numbers.

To the level of an orbital, this comes down to one of the two electrons that share an orbital having spin-up, which is given by the spin quantum number `m_s = +1/2`, and the other having spin-down, which is given by `m_s = -1/2`.

Now, the `4p` subshell contains a total of three `4p` orbitals, `4p_x`, `4p_y`, and `4p_z`.

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Since each of those `p` orbitals can hold a maximum of two electrons, the `p` subshell can hold a maximum of

`3 color(red)(cancel(color(black)("p orbitals"))) * "2 e"^(-)/(1color(red)(cancel(color(black)("p orbital")))) = "6 e"^(-)`

Therefore, you can say that a `4p` orbital can hold a maximum of two electrons and the `4p` subshell can hold a maximum of six electrons.