The first orbital, also known as the 1s orbital, can hold a maximum of 2 electrons.
This limitation is due to the Pauli Exclusion Principle, which states that no two electrons can have the same set of quantum numbers. Since the 1s orbital can be fully described by two quantum numbers, it can accommodate only two electrons, each with opposite spins. Therefore, in the simplest terms, the first orbital is the closest to the nucleus of an atom and can hold a total of two electrons.