Here's why:

* Subshells: Atoms have different energy levels called shells. Each shell is divided into subshells (s, p, d, f).

* Electron Capacity: Each subshell has a specific number of orbitals, and each orbital can hold up to 2 electrons.

* p Subshell: The p subshell has 3 orbitals, meaning it can hold a maximum of 6 electrons (3 orbitals x 2 electrons per orbital). However, in a neutral atom, a p subshell is considered "full" when it has 8 electrons.

Let me know if you'd like more details on electron configurations!