Final answer:
A nonpolar covalent bond occurs when electrons are shared equally between two atoms, often of the same element, as seen in O₂, H₂, Cl₂, or symmetric compounds like CH₄.
Step-by-step explanation:
A nonpolar covalent bond is one in which the electrons are shared equally between two atoms. This typically occurs when the atoms involved are of the same element, or when their electronegativity values are very close. A prime example of this would be a diatomic oxygen molecule (O₂), where the electrons distribute equally between the two oxygen atoms, resulting in a nonpolar covalent bond. Other examples include diatomic molecules such as hydrogen (H₂) or chlorine (Cl₂), and certain symmetrical compounds such as methane (CH₄), where the electrons are shared equally between the central carbon atom and the surrounding hydrogen atoms.