Here's why:
* Electron Configuration: Gallium's electron configuration is [Ar] 3d10 4s2 4p1.
* Valence Shell: The outermost shell, the 4th shell in this case, contains the valence electrons.
* Valence Electrons: The 4th shell has a total of 3 electrons (2 from 4s and 1 from 4p), which are the valence electrons.
