Those last 3 electrons are therefore the valence of Gallium (exactly like the valence of Aluminum, which is also 3). This means that Gallium, like Aluminum will be ready to lose 3 electrons and have a +3 charge, therefore it is a cation.

Does gallium lose valence electrons?

Gallium has the following electron configuration: \begin{align*}\text{[Ar]}4s^23d^{10}4p^1\end{align*}. The 4s and 4p electrons can be lost in a chemical reaction, but the electrons in the filled 3d subshell cannot. Gallium therefore has three valence electrons.

What happens to gallium electrons?

Gallium is in Group 13. It has 31 electrons. We form cations by removing electrons first from the outermost p orbitals, followed by the s orbital and finally the d orbitals (if any more electrons need to be removed).