Question

What is the valency of sulphate $(S{O_4})$ ?

Answer 1

Valency can be defined as the number of hydrogen atoms which combine directly or indirectly with one atom of an element. Valency is the combining capacity of an atom of an element to form a chemical bond. It is related to the number of electrons that are present in the outermost shell.

Complete answer:
Valency is the capacity of an atom or a molecule to combine. There are different types of ways to assess the valency of a specific atom: The modern periodic table consists of components organized in such a way that it is possible to find the valency of a given element. Metals have a valency of $+ 1$ in the first column whereas the noble gases have a valency of $0$ in column $18$ and they are inert. Sulphate ion is an anion derived from the sulphuric acid in which the valency of the hydrogen atom is one. As hydrogen is more electropositive than sulphate, $+ 1$ will be its oxidation number. Consider the oxidation number of sulphate as $x$ . We know that the sum of oxidation numbers is zero.
So, we have $2 \times 1 + 1 \times x = 0$
$x = - 2$
Therefore, the valency of sulphate is $2$ .

Note:
A given compound is said to be stable if it follows the octet rule i.e. if the compound has eight electrons in its outermost shell. Valency can also be determined from the chemical formula. It depends on the octet rule and the valency can be found by examining the combining capacity of an element.