Hapetustilat

Hapetustilat, or oxidation states, are the formal charges assigned to atoms in chemical compounds under a standard set of rules that treats bonds as ionic and assigns shared electrons to the more electronegative atom. These states are a bookkeeping device used to describe electron transfer during redox reactions rather than a direct measure of actual charge distribution.

Key rules underpinning hapetustilat include: the oxidation state of a free element is 0; monoatomic ions have oxidation states equal to their charge; in most compounds hydrogen is +1 and oxygen is −2; fluorine is always −1; other halogens are usually −1 unless bound to fluorine or oxygen; the sum of oxidation states in a neutral compound is 0 (or the total charge in ions); alkali metals are +1 and alkaline earth metals are +2; carbon and many other elements can assume multiple states from negative to positive values.

Examples help illustrate the concept. In sodium chloride (NaCl), Na has +1 and Cl has −1; in water (H2O) hydrogen is +1 and oxygen is −2; in carbon dioxide (CO2) carbon is +4 and oxygen is −2; in potassium permanganate (KMnO4), manganese is +7. Transition metals commonly exhibit several hapetustilat, such as iron in Fe2O3 (+3) or Mn in KMnO4 (+7).

Limitations include that hapetustilat are formal numbers, not direct measurements of electron density, and they can vary with the chemical environment, especially in coordination compounds or complex ions. They remain a central tool in redox chemistry, inorganic nomenclature, and materials science for describing and predicting reactivity.