Question

How to find valency?

Answer 1

Different ways to determine valency

1. The combining capacity of an element is called its valency. Different ways to determine valencies are given below.
2. According to the octet rule, a compound is said to be stable when the outermost shell of the compound is having eight electrons.
3. If the number of electrons in the outer shell is between one to four, the compound is said to have positive valency.
4. Valency is equal to the number of electrons in its outermost shell when the outermost shell has electrons $4$ or less than $4$.
5. If the number of electrons in the outer shell is four to eight, the compound is said to have negative valency.
6. The valency is therefore determined by subtracting the number of valence electrons from $8$ for elements having valence electrons more than $4$
7. A periodic table consists of elements that are arranged in such a way that, the valency of a given element can be determined.
8. In the periodic table metal of Group one has a valency of $1$, Group 2 has a valency of $2$, and group $18$ the valency should be zero, hence valency can be determined using the arrangement of atoms in the periodic table.
9. Finding valency from the chemical formula is based on the octet rule, and by observing the combination of an element, the valency can be determined.
10. Example: Carbon has an atomic number$=6$ and its electronic configuration is$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^2$, therefore the number of valence electrons$=4$. Valency$=8-4\Rightarrow 4$.

Therefore, from the following above rules, valency is determined.