Oksidaatiovaiheen

Oksidaatiovaihe, often translated as oxidation state, is a conceptual tool used in chemistry to describe the hypothetical charge an atom would have if all of its bonds to different atoms were fully ionic. It is not a real charge, but rather a bookkeeping method to track electron transfers in redox reactions. In this system, electrons are assigned to the more electronegative atom in a bond. The oxidation state of an atom in a molecule or ion is the sum of the oxidation states of all atoms within it, which must equal the overall charge of the species.

There are a set of rules used to assign oxidation states. For example, the oxidation state of an element in its elemental form is always zero. Fluorine always has an oxidation state of -1 in compounds. Oxygen usually has an oxidation state of -2, except in peroxides where it is -1 and when bonded to fluorine. Hydrogen typically has an oxidation state of +1 when bonded to nonmetals and -1 when bonded to metals. Halogens generally have an oxidation state of -1, unless bonded to oxygen or a more electronegative halogen.

The concept of oxidation state is crucial for understanding and balancing redox (reduction-oxidation) reactions. In these reactions, electrons are transferred between chemical species, leading to changes in their oxidation states. Oxidation is defined as an increase in oxidation state (loss of electrons), while reduction is a decrease in oxidation state (gain of electrons). By tracking these changes, chemists can predict reaction outcomes and design chemical processes.