Which of 2 of these will have a single covalent bond? N2, H2, O2, F2

H2 & F2

Explanation:

A covalent bond is formed when an electron is shared between two atoms. The two electrons of the covalent bond are positioned between the nuclei of the both bonding atoms. The electron pair of the bond may be equidistant from the nucleus of the two atoms or nearer to the nucleus of one of the bonding atoms than the other depending on the relative electro negativities of the both bonding atoms.

For homonuclear covalent bonds, there is no electro negativity difference between the bonding atoms. A single line may be used to indicate the shared electron pair between the two atoms.

Hydrogen and fluorine form homonuclear covalent diatomic compounds in which only a single electron pair is shared between bonding atoms. A single covalent bond is found connecting the two bonding atoms, hence the answer.