Valency is known as the capacity of an atom or a molecule to combine. There are various ways to assess a specific atom’s valency, and they are:
- The periodic table consists of components organized in such a way that it is possible to determine the valency of a given element. Metals have a valency of +1 in column 1 whereas the noble gases have a valency of 0 in column 18 and they are inert.
- Valency from the chemical formula is depended on the octet rule and by examining the combining of an element, the valency can be identified.
- A compound is said to be stable as per the octet rule, whenever the compound’s outermost shell has eight electrons. The substance is said to have positive valency if the number of electrons in the outer shell is between one to four. The valency is calculated for compounds with electrons four, five, six, or seven by subtracting the electron from eight. Apart from Helium, all noble gases have eight electrons.
Let us find the valency of nitrate
NO3 (Nitrate ion) has three oxygen and one nitrogen atom.
Nitrogen belongs to group -15 in the periodic table and it forms bonds with three oxygen atom with +5 charge.
Oxygen belongs to the group – 16 in the periodic table, thus it has a valency f -2.
So, the valency of nitrate ion is
5 – [3 ✕ 2]
⇒ 5 – 6