* Electron Configuration: The electron configuration of gallium is [Ar] 3d10 4s2 4p1.
* Outer Shell: The outermost shell for gallium is the 4th shell (n=4).
* Valence Electrons: The electrons in the outermost shell are called valence electrons. In this case, there are 3 valence electrons (2 in 4s and 1 in 4p).
* Most Reactive Electron: While gallium has three valence electrons, the one in the 4p subshell is the most reactive and participates in chemical bonding.
Therefore, when considering the outer shell for chemical bonding, gallium effectively acts as though it has 1 electron in its outer shell.
