A polar (polarised) covalent bond is a bond in which the electrons are shared unequally, because the two atoms differ in electronegativity. The more electronegative atom draws the electrons towards itself, giving it a partial negative charge and the other atom a partial positive charge. The H–Cl bond is polar, in contrast to a nonpolar covalent bond, where sharing is equal.

极性(极化)共价键是电子被不均等共享的键,这是因为两个原子电负性不同。电负性较大的原子把电子拉向自己,使其带部分负电荷,而另一原子带部分正电荷。H–Cl 键是极性的;与之相对的是均等共享的非极性共价键。