The order of increasing energy is: 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < ...
Water (Hâ‚‚O): Oxygen shares one electron with each of the two hydrogen atoms. Each hydrogen atom contributes one electron, ...