The two electrons from oxygen's outer shell are shared with two electrons from both hydrogens as they bond together, and the remaining four outer shell electrons from oxygen form two pairs.

来自氧原子外壳的两个电子通过分享分别来自两个氢原子上的两个电子使氢原子和氧原子键合在一起，氧原子外壳上剩下的四个电子分别组成两对。