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Pt) and the elements О, F, Вr, whose oxidation state is always lower than the

group number.

The notion of the oxidation state should not be confused with the valence of atoms,

even in cases where their absolute values coincide accidentally. Valence is

determined by the number of bonds that connect this atom with others, and

therefore it cannot have a plus or minus sign, or be equal to zero. For example, the

oxidation state of Carbon in methane CH 4, methanol CH 3OH, formaldehyde of

НСОН and Carbon (IV) oxide of CO 2 are -4, -2, 0, and +4 respectively, while the

valence of Carbon in all of these compounds is equal to four. It should be noted

that the oxidation state also has nothing to do with the actual, or effective, charge

of atoms in the compounds. For example, in Chromium (III) СrСl 3 chloride the

effective charge of Chromium is +1.2, while the oxidation state is +3. Even

greater difference between these values exists in the compound К 2СrО 4: while the
oxidation state is +6, the effective charge of chromium is only + 0.2.

Despite the fact that the oxidation state is a conditional notion and formal to some
extent, it has become widely used in the classification of chemical processes, while

considering the oxidation-reducing properties of substances, and in calculating the
coefficients in reduction- oxidation reactions.

6.2 General concepts of oxidation-reduction processes

Reactions that are accompanied by a change in the oxidation state of reactants

atoms are called reduction-oxidation (redox).

Atoms, ions, or molecules that give away electrons (increase the oxidation state),

are called reducing agents. The reducing agents are oxidized during the reaction.

Atoms, molecules, or ions that connect electrons (reduce the oxidation state) are

called oxidants. During the reaction they are restored.

The process of electrons joining an atom, molecule, or ion is called reduction.

The process of losing electron is called oxidation. The number of electrons given

by the reductant must be equal to the number of electrons that the oxidizer

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