Final answer:
Diatomic elements, which are made up of two atoms of the same element, form nonpolar covalent bonds as they share electrons equally with no difference in electronegativity.
Step-by-step explanation:
The type of bond that diatomic elements should form is a nonpolar covalent bond. Diatomic elements, such as molecular oxygen (O₂), consist of two atoms of the same element that share the electrons equally. This evenly shared electron distribution indicates that there is no difference in electronegativity between the two atoms, resulting in a bond where there is no charge separation and thus categorizes the bond as nonpolar covalent.