Hapetustila

Hapetustila is a term used in Finnish chemistry to denote the oxidation state of an atom within a chemical species. It indicates the degree to which an atom has lost or gained electrons relative to its neutral elemental form.

In practice, hapetustila is roughly equivalent to the oxidation state or oxidation number used in English-language chemistry. The concept serves as an accounting method for electron transfer in redox reactions and is common in Finnish textbooks, problem sets, and scientific literature.

Determining hapetustila relies on standard rules: the total of oxidation states in a neutral molecule is zero; in a polyatomic ion the sum equals the ion’s charge. General conventions include: oxygen typically −2, hydrogen usually +1, fluorine −1, alkali metals +1, and alkaline earth metals +2. The oxidation state of an element in a complex or compound is assigned so that the sum of all oxidation states matches the overall charge of the species.

Examples help illustrate the idea. In water (H2O), hydrogen is +1 and oxygen is −2, giving a total of zero. In nitrate (NO3−), nitrogen is in the +5 oxidation state. In iron(III) oxide (Fe2O3), each iron is +3. These assignments aid in balancing redox equations and in predicting electron transfer behavior in reactions and biological systems.

Differences with related concepts: hapetustila refers to a formal accounting of oxidation state, not to the actual electron density distribution, which can involve partial charges and resonance. In Finnish usage, hapetustila is standard terminology for general chemistry, with hapetusluku used in some contexts. See also oxidation state, oxidation number, redox reactions.