The complete question is found on the image attached.
Answer:
a) Rb= +1, Br= -1
b)Bromide and rubidium ions are related to krypton
c) C
Explanation:
Rubidium is found in group 1 with a charge of +1. Bromine is found in group 17 with a charge of -1. Both species have the same configuration as krypton. The ionic sizes of the ions are a very similar to each other Rb+ is 166 while Be is 167.
This RbBr is an ionic compound.