Diatomic molecules will be nonpolar when 1) a pair of shared electrons is located closer to one atom than the other 2) both atoms are the same element 3)there is a difference in electronegativity 4) atoms have a different number of protons

2) both atoms are the same element

Explanation:

A polar covalent bond is defined as the bond which is formed when there is a difference of electronegativities between the atoms. It is also defined as the bond which is formed due to the unequal sharing of electrons between the atoms.

Non-polar covalent bond is defined as the bond which is formed when there is no difference of electronegativities between the atoms. It is also defined as the bond which is formed due to the equal sharing of electrons between the atoms.  

Diatomic molecules when made up of two atoms of same element will form non polar covalent bond as there is no electronegativity difference.

1. a)c-14 has two more protons

2. d)they have different numbers of protons, neutrons, and valence electrons; they are all gases at room temperature.

3. c) iron and nickel.