According to the Pauli exclusion principle, which is a fundamental principle of quantum mechanics, each orbital can hold a maximum of two electrons. These electrons must have opposite spins, meaning they have opposite values for their intrinsic angular momentum, or "spin."
This principle arises from the quantum mechanical properties of electrons. In an atom, electrons occupy different energy levels and sublevels, which are represented by orbitals. Each orbital has a unique set of quantum numbers that describe its energy, shape, and orientation in space.
Since there are only two possible spin states for an electron (often labeled as "spin-up" and "spin-down"), each orbital can accommodate a maximum of two electrons, with their spins paired. This is known as the Pauli exclusion principle, and it ensures that no two electrons within an atom can have the same set of quantum numbers, preventing them from occupying the same orbital with the same spin.
The maximum number of electrons that can be accommodated in each type of orbital is as follows:
- s orbital: 2 electrons
- p orbital: 6 electrons (3 orbitals, each holding 2 electrons)
- d orbital: 10 electrons (5 orbitals, each holding 2 electrons)
- f orbital: 14 electrons (7 orbitals, each holding 2 electrons)
It's important to note that while these numbers represent the maximum capacity of each orbital, the actual number of electrons in an orbital depends on the electron configuration of the atom or molecule in question.