In determining the oxidation is necessary to know that the higher the degree of oxidation of the metal corresponds to the number of t
he periodic system, which is the element.But this rule has exceptions.
the degree of oxidation of non-metals when connecting them to the metal atoms are always negative, and when combined with non-metal atoms, there may be negative and positive.Higher negative oxidation state of non-metals can be found by subtracting the number of the group of 8, which is the element.Higher positive is the number of electrons in the outer layer (the number of electrons corresponds to the number of the group).
The oxidation of simple substance, whether it is metal or nonmetal, is always equal to zero.In the molecules of the algebraic sum of the powers of the elements according to the number of atoms is zero.
To determine the extent of any element in the mix, it is also necessary to remember that hydrogen has an oxidation state in compounds (1).Eliminating hydrides (hydrogen compounds with metals of main group of the first-second group, the oxidation state 1, such as Na + H-);is oxygen (-2), except for oxygen with fluorine compound + O 2 F-2 and peroxide (H2O2 - oxidation of oxygen (-1) is fluoro (-1).
exampleshould determine the degree of oxidation of elements in the molecule of potassium dichromate (potassium dichromate), the formula of which K2Cr2O7.U two chemical elements potassium and oxygen, they are constant and equal to 1 and -2. The degrees of oxidation in oxygen is (-2) • 7 =(-14) have potassium (+1) = 2 • (+ 2). The number of positive number equal to negative. Thus (-14) + (+2) = (- 12). Hence the number of atom of chromium equal to 12 degrees positivebut atoms 2, it means that one atom has to (12): 2 = (+6), write down the degree of oxidation of elements: K + 12Cr + 6 2O-2 7.