which pair of atom will combine chemically to give an ionic compound?

Question

a)H and U
b)O and S
C)F and CA
d)NA and CL

Answer 1

I don't know a CA, NA, or CL.
Look up the electronegativities of each element pair. Subtract the larger from the smaller. If the difference is 1.8 or so higher it is classified as an ionic bond.