What do the following have in common: MgCl2, AlF3, CaI2, KCl
Choose all that apply.
They are nonpolar in nature.
They are salts.
They are all ionic compounds.
They are all molecular compounds.

They are salts, ionic compounds

Explanation:

To know if they are covalent or ionic we need to check their difference in electronegativity. As an example mgcl2, mg has electronegativity of 1.2 and cl 3 so 3-1.2=1.8 which is bigger than 1.7 means it's ionic therefore they are salts

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6