hapetuspitoisuuden

Hapetuspitoisuuden, often translated as oxidation state or oxidation number, is a concept used in chemistry to describe the hypothetical charge that an atom would have if all its bonds to atoms of different elements were fully ionic. It is a bookkeeping tool that helps track the movement of electrons in chemical reactions, particularly in redox (reduction-oxidation) reactions.

In a neutral atom, the oxidation state is zero. For ions, the oxidation state is equal to the charge of the ion. When atoms combine to form compounds, rules are applied to assign oxidation states. For example, oxygen in most compounds has an oxidation state of -2, and hydrogen typically has an oxidation state of +1 when bonded to nonmetals. The sum of the oxidation states of all atoms in a neutral molecule must be zero, and in a polyatomic ion, it must equal the charge of the ion.

Understanding oxidation states is crucial for balancing redox equations and predicting the reactivity of substances. It helps identify which species are being oxidized (losing electrons, increasing oxidation state) and which are being reduced (gaining electrons, decreasing oxidation state). For instance, in the reaction of iron rusting, the iron metal (oxidation state 0) is oxidized to iron(III) oxide (where iron has an oxidation state of +3), and oxygen is reduced.