Here's why:
* Fluorine's electron configuration: Fluorine has 9 electrons, with the configuration 1s² 2s² 2p⁵. This means it has 5 electrons in its 2p subshell, which can hold a maximum of 6 electrons.
* Sodium's electron configuration: Sodium has 11 electrons, with the configuration 1s² 2s² 2p⁶ 3s¹. It has a single electron in its 3s orbital, which is further away from the nucleus and has a higher energy level than the 2p orbitals.
* Ionic bond: When sodium loses its 3s electron to fluorine, it becomes a positively charged ion (Na⁺). Fluorine gains this electron, completing its 2p subshell and becoming a negatively charged ion (F⁻). This transfer of electrons forms an ionic bond between the two atoms.
Therefore, the 2p orbital of fluorine is being filled when it accepts an electron from sodium.
