Which pair of atoms is most likely to be covalently bonded?

1) Na and O

2) K and F

3) Ne and O

4) C and S

1 and 2 are a metal - nonmetal pair - that kinda means ionic bond. Na and F are going to lose electrons.

3 [Nonmetals bond to each other covalently! Ne and O are nonmetals. O would need 2e to become stable. Either getting 2e (ionic bond) or sharing 2e (with H, for example). However, Ne is a noble gas, which means it is already doing fine with its 8e on its valence shell and isn't gonna share 2e of its electrons with O. So, despite the fact that they are both nonmetals, they won't form a covalent bond.

Sum up: they are 2 gases haha, and one of them is a noble one. They will never bond to each other covalently

4 - C and S - right answer

As they are both nonmetals (nonmetals bond to each other covalently, none of them is a noble gas, and so on)

1) Na and O - ion bond

2) K and F - ion bond

3) Ne and O - no bond (as Ne is a noble gas)

And by elimination, your answer is 4)