Question

How do you calculate the formal charge of Cl in $Cl{{O}^{-}}$ and $ClO_{3}^{-}$ ?

Answer 1

Hint As we know that formal charge is the charge which is basically assigned to an atom in a molecule, by assuming that electrons are equally shared in all chemical bonds between atoms, irrespective of the relative electronegativity.

Complete Step by step solution:
- As we know that oxygen has a formal charge of -2 in general, whereas chlorine is found to have variable formal charge.
- Let us first find out the formal charge of Cl in $Cl{{O}^{-}}$ as:
Firstly, let us consider the formal charge of Cl in $Cl{{O}^{-}}$ be x.
Now, by charge conservation method we can write:
$Cl{{O}^{-}}$
x – 2 = -1
x = +1
- Hence, the formal charge of Cl in $Cl{{O}^{-}}$ is +1.
- Let us now find out the formal charge of Cl in $ClO_{3}^{-}$ as:
Firstly, let us consider the formal charge of Cl in $ClO_{3}^{-}$be y.
Now, by charge conservation method we can write:
$ClO_{3}^{-}$
y + ( -2 X 3) = -1
y = +5
- Hence, the formal charge of Cl in $ClO_{3}^{-}$ is +5.
- Hence, we can conclude that the formal charge of Cl in $Cl{{O}^{-}}$ is +1 and in $ClO_{3}^{-}$ is +5.

Note:
- As we know that in determining the best Lewis structure or we can say the predominant resonance structure for a molecule, the structure is chosen in a way that the formal charge on each of the atoms is nearly as close to zero as possible.