Question

which of the following diatomic molecules is joined by a double covalent bond?
he₂
cl₂
n₂
o₂

Explanation:

Helium (He) is a noble - gas and does not form compounds easily. Chlorine ($Cl_2$) has a single covalent bond between its atoms ($Cl - Cl$). Nitrogen ($N_2$) has a triple covalent bond ($N\equiv N$). Oxygen ($O_2$) has a double covalent bond ($O = O$) as each oxygen atom shares two pairs of electrons to complete its octet.

Answer:

D. $O_2$