Oxidation state

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Plutonium ions in several oxidation states

Oxidation state refers to the number of electrons added to or removed from an element. Sodium metal, for example, has an oxidation state of 0 in the elemental state. But when it gives up its one valence (outer) electron (symbolized by e-), it becomes a sodium ion with an oxidation state of +1. Iron is another example. It can lose two electrons, forming an oxidation state of +2; or it can lose 3, forming an oxidation state of +3.

If elements gain electrons, they have negative oxidation states. If chlorine gains an electron, it forms a -1 ion. If sulfur gains two electrons, it forms a -2 ion.

The oxidation state determines the number of atoms of other elements that can bind to the atom.

All elements have an oxidation state of 0.