Valence bond theory is a quantum-mechanical model in which a covalent bond forms when an atomic orbital of one atom overlaps with an atomic orbital of another, and the two orbitals share a pair of electrons. The bond is localised between the two atoms, and its strength depends on the extent of overlap. The theory is often combined with the idea of hybridisation to account for molecular shapes.

价键理论是一种量子力学模型,认为当一个原子的原子轨道与另一原子的原子轨道重叠、两轨道共享一对电子时,即形成共价键。该键局限于两原子之间,其强度取决于重叠的程度。该理论常与杂化的概念结合,以解释分子的形状。