Final answer:
The electron configuration of ground-state gallium (Ga) is [Ar]4s²3d±4p¹, and it tends to form a Ga³⁺ ion with [Ar]3d±⁰ configuration.
Step-by-step explanation:
The full electron configuration of a ground-state atom of gallium (Ga) can be written as [Ar]4s²3d±4p¹. Gallium, whose atomic number (Z) is 31, follows zinc (Z=30) in the periodic table and is located just after the first row of transition metals. The complete d sublevel (3d±⁰) in gallium provides a shielding effect for the valence electron in the 4p orbital, making its first ionization energy relatively low. This chemistry contributes to the formation of a Ga³⁺ ion with a pseudo noble gas configuration of [Ar]3d±⁰, which is particularly stable.