concept of valence became a chemistry in the nineteenth century, then for her unit was adopted by the valence of the hydrogen atom.Valence another element can be defined as the number of hydrogen atoms, which attaches itself to one atom of another substance.Similarly valence determined by the valence of hydrogen to oxygen, which is usually equal to two, and thus to determine the valence of the other elements in compounds with oxygen by simple arithmetic operations.Valence element oxygen is equal to twice the number of oxygen atoms, which can be attached one atom of the element .
to determine the valence element can also use the formula.
It is known that there is a relationship between the valence element , its equivalent weight and the molecular weight of its atoms.The relationship between these qualities expressed by the formula: Valence = molar mass of atoms / equivalent weight.Since the equivalent weight - it is the amount that is necessary to replace one mole of hydrogen or to react with one mole of hydrogen, the larger molar mass compared to the mass equivalent, the greater the number of hydrogen atoms may replace or attach to themselves atom element and therefore the higher valence.
connection between chemical element of a different nature.This can be a covalent bond, ionic, metallic.For bonding atom must have: an electric charge, an unpaired valence electron, the free valence orbitals, or unshared pair of valence electrons.Together, these features determine the valence state and stretching the ability of an atom.
Knowing the number of electrons in the atom, which is equal to the serial number element in the periodic table of elements, guided by the principle of minimum energy, the Pauli exclusion principle and Hund's rule can construct the electronic configuration of the atom.These constructions will analyze the possibility of the valence of the atom.In all cases, primarily realizes the possibility of forming a bond due to the presence of unpaired valence electrons, valence additional capabilities, such as a free lone pair orbital or valence electrons may be frustrated if it is insufficient energii.I the foregoing it can be concluded thateasiest to determine the valence atom in any combination, and much more difficult to determine the ability of atoms valency.But practice makes simple and it is.