Final answer:
When two atoms have similar electronegativity, they share electrons equally, forming a nonpolar covalent bond because neither atom can attract the shared electrons much more strongly than the other.
Step-by-step explanation:
When two atoms have similar electronegativity, the electrons in the bond between them are shared equally. This type of sharing leads to what is called a nonpolar covalent bond. In nonpolar covalent bonds, there is an even distribution of electrical charge across the molecule because the electrons are not drawn more strongly to one atom than to the other.
Electronegativity is an atom's ability to attract and hold onto electrons; when the difference in electronegativity between two bonded atoms is small, neither can significantly attract the shared electrons away from the other, resulting in equal sharing. If bonded atoms are identical, as in H2 or O2, they have the same electronegativity and will always share electrons equally. However, if there is a slight difference in electronegativity but not enough to cause total electron transfer, a nonpolar covalent bond also forms.