Answer:
The formula of ionic compound rubidium nitride is Rb3N.
Step-by-step explanation:
Rubidium (Rb) is a group 1 alkali metal, which means it has a charge of +1 when it forms an ion. Nitrogen (N) is a group 15 element and tends to gain three electrons to achieve a stable octet configuration, resulting in a charge of -3 when it forms an ion.