The valency chart consists of a complete list of the valencies of that element. The chemical formula of an element is determined on the basis of the valencies of its compound. Valency can be defined as the combining capacity of an element. It is always a whole number and does not have a plus or minus sign. The electrons present in the outermost shell of an atom are known as valence electrons, and so in that context, valency can be defined as the number of electrons an element can lose or gain to attain stability. A valency chart is referred to when writing the chemical formula of a compound, which means that by referring to the valency, it is possible to know how the atoms of an element will combine with atoms of another element.
Electrons are arranged in atoms in such a way that they revolve around the nucleus in different orbitals or ‘shells’. These orbitals are represented as K, L, M, N, etc. The valence electron of atoms remains in the outermost shell of electrons. These outermost shell electrons take part in the chemical reaction as they generally contain more energy than the electrons present in other orbits.
The valency or valency chart is helpful in determining how many atoms of an element will combine with another element in order to form a chemical formula. Another important use of valency is to find or deduce the formulae of compounds. If the valency of elements is known, then it is easy to write the formulae of compounds of those elements.
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