with an atom that donates a valence electron to complete chlorine's outer shell. However, chlorine can also have oxidation states from +1 to +7 and can form more than one bond by donating valence electrons. Hydrogen has only one valence electron, but it can form bonds with more than one atom. In the bifluoride ion (), for example, it forms a three-center four-electron bond with two fluoride atoms: Another example is the three-center two-electron bond in diborane (). Maximum valences of the elements Maximum valences for the elements are based on the data from list of oxidation states of the elements. They are shown by the color code at the bottom of the table. See also Abegg's rule Oxidation state References Chemical bonding Chemical properties Dimensionless numbers of chemistry