Question

Calculate the valency of $O$ in $S{O_3}$.

Answer 1

Hint: Valency is the capacity of an atom to bond with another atom or molecule. Valence electrons are the electrons of the outermost shell of an atom. The valence electrons participate in any chemical reaction.

Complete step by step answer:
-Here given molecule is $S{O_3}$.
We have to find the valency of oxygen atoms in this molecule.
One of the methods to find valency is -
 On the basis of Chemical Formulae- The valency of an element can also be determined from chemical formula. It is achieved by observing how elements form bonds and combine with each other. It is based on the octet rule. Using this method-
First determine the number of elements combined. Here one sulphur atom combines with $3$ oxygen atoms.
We know that Electronic configuration of sulphur is $S = 2,8,6$ and oxygen is $O = 2,6$
Here oxygen only needs two electrons to fill its octet so the three oxygen atoms share their $2$ electrons each with $6$ electrons of sulphur forming a double bond between them.

Hence the valency of oxygen atom in a given molecule is $2$.

Additional Information:
Octet rule-
The Bohr-buy scheme states that the outermost orbit of an atom can have a maximum eight electrons. The tendency of an atom to obtain eight electrons in its outermost orbit by gaining or losing electrons is called octet rule. The atom whose octet is complete is most stable. If the number of electrons in the outermost shell is \[4\] or less then the valency of the atom is equal to this number.
If the number of electrons is more than \[4\] then, it will be easier for the atom to accept electrons than donating it. So we can find valency by this formula-
$ \Rightarrow $ Valency=$8$$ - $ the number of valence electrons

Note:
The uses of valency-
-It helps in determining the chemical formula of a molecule.
-It helps in determining the number of atoms of an element that combine with another element to form a molecule.