Oksüdatsioonitasem

Oksüdatsioonitasem, also known as oxidation state or oxidation number, is a conceptual tool used in chemistry to describe the degree of oxidation of an atom in a molecule or ion. It represents the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. This means that the more electronegative atom in a bond is considered to have "taken" all the bonding electrons, while the less electronegative atom is considered to have "lost" them.

The oxidation state of an atom can be a positive, negative, or zero integer. Pure elements in their standard state have an oxidation state of zero. For ions, the oxidation state is equal to the charge of the ion. For example, in the sodium ion (Na+), sodium has an oxidation state of +1. In the chloride ion (Cl-), chlorine has an oxidation state of -1.

In compounds, oxidation states are assigned based on a set of rules. For instance, oxygen typically has an oxidation state of -2, except in peroxides where it is -1, and when bonded to fluorine. Hydrogen usually has an oxidation state of +1 when bonded to nonmetals and -1 when bonded to metals. The sum of the oxidation states of all atoms in a neutral molecule must equal zero. In a polyatomic ion, the sum of the oxidation states must equal the overall charge of the ion.

Understanding oxidation states is crucial for balancing redox (reduction-oxidation) reactions, where electrons are transferred between chemical species. It helps to identify which species are being oxidized (losing electrons, increasing oxidation state) and which are being reduced (gaining electrons, decreasing oxidation state).