A homonuclear diatomic molecule is a diatomic molecule in which both atoms are of the same element. Because the two atoms are identical, their atomic orbitals contribute equally to each molecular orbital. Hydrogen (H₂), oxygen (O₂), and nitrogen (N₂) are examples; they contrast with heteronuclear diatomic molecules, whose two atoms differ.

同核双原子分子是两个原子为同种元素的双原子分子。由于两原子相同,它们的原子轨道对每个分子轨道的贡献相等。氢(H₂)、氧(O₂)和氮(N₂)都是例子;它们与两原子不同的异核双原子分子相对。