* Ionic Bonding: Ionic bonds occur between metals and nonmetals. Metals tend to lose electrons and become positively charged cations, while nonmetals tend to gain electrons and become negatively charged anions.

* Electronegativity: Electronegativity is a measure of an atom's ability to attract electrons. A large difference in electronegativity between two atoms indicates a higher likelihood of ionic bonding.

Let's analyze the options:

* Ni (Nickel): Nickel is a transition metal, and while it can form ionic bonds, it's more likely to form covalent bonds.

* Cu (Copper): Copper is also a transition metal, and similar to nickel, it tends to form covalent bonds.

* Ga (Gallium): Gallium is a metalloid, meaning it has properties of both metals and nonmetals. It's more likely to form covalent bonds.

* Rb (Rubidium): Rubidium is an alkali metal. Alkali metals are highly reactive and readily lose one electron to form a +1 cation. Chlorine is a halogen and readily gains one electron to form a -1 anion. This large electronegativity difference leads to a strong ionic bond.

Therefore, chlorine will ionically bond with rubidium to form RbCl (Rubidium Chloride).