Oxidationsniveau

Oxidationsniveau, also known as oxidation state, is a bookkeeping concept in chemistry used to describe the apparent oxidation of an atom within a compound or ion. It assigns a formal charge to each atom according to a fixed set of rules, enabling comparison of oxidation across elements and the tracking of electron transfer in redox processes. It is a formalism, not a direct measure of actual electron density around the atom.

Rules for assignment include that the sum of the oxidation numbers in a neutral compound is zero, and in an ion it equals the ion’s charge. Elements in their standard states have oxidation number zero. Fluorine is always -1 in compounds; hydrogen is usually +1 (except in hydrides, where it is -1); oxygen is usually -2 (peroxides have -1). Alkali metals are +1 and alkaline earth metals are +2. In polyatomic ions, the sum of the oxidation numbers equals the ion’s charge. In covalent bonds, electrons are allocated to the more electronegative atom, but the assignment remains a formal accounting method.

Examples illustrate the concept: in water (H2O), hydrogen is +1 and oxygen is -2; in ammonia (NH3), nitrogen is -3 and each hydrogen is +1; in iron(III) oxide (Fe2O3), iron is +3 and oxygen is -2; in carbon dioxide (CO2), carbon is +4 and each oxygen is -2. These numbers help determine how electrons are redistributed during reactions.

Oxidationsniveau is widely used to balance redox equations, assess electron transfer in reactions, and analyze oxidation states in coordination chemistry and electrochemistry. Limitations include that oxidation numbers are a formalism and may not reflect real electron density, especially in covalent or delocalized systems, or in metals with fractional or mixed valence states.