Question

How many hybrid orbitals are there in ${\mathrm{HNO}}_3$?

Answer 1

Hybrid orbitals in ${\mathrm{HNO}}_3$:

• Hybrid orbitals are formed by the combination of atomic orbitals of similar energy of valence shell of the same atom.
• The no. of hybridized orbitals of an atom is equal to the no. of orbitals of similar energy of valence shell undergoing hybridization.
• For example: If one 4s orbital and three 4p orbitals are undergoing hybridization, then there will be a total of 1(one 4s)+3(three 4p) = 4 hybridized orbitals and it will be known as $\text{s}{\text{p}}^{\text{3}}$ hybridization.
• we can calculate the no. of hybridized orbitals within the molecule by knowing the hybridization of each atom present in it.
• We can calculate the hybridization of each atom in a molecule by drawing the lewis structure of that molecule.
• Hydrogen has only 1 2s orbital, hence it cannot undergo hybridization.
• We can draw the structure of $\text{HN}{\text{O}}_{\text{3}}$ which is the hybrid of two resonance structures, which can be shown as follow:

• From the given figure, the hybridization of a nitrogen atom ($\text{N}$) is $\text{s}{\text{p}}^{\text{2}}$, which represents that, three hybrid orbitals are present in nitrogen, as it has three sigma bonds connected to it.
• Also, hybridization of the oxygen atom ($\text{O}$) atom which is bonded with the hydrogen atom ($\text{H}$) atom is $\text{s}{\text{p}}^{\text{3}}$, represents the oxygen atom has four hybrid orbitals are present as it has two sigma bonds and two lone pairs of electrons in it.
• However the other two oxygen atoms are showing resonance in the Lewis dot structure hence, these two oxygen are equivalent to each other showing the same hybridization which is $\text{s}{\text{p}}^{\text{2}}$, which means they have three hybrid orbitals within them.
• Hence, the total hybrid orbitals present in $\text{HN}{\text{O}}_{\text{3}}$ = Hybridized orbitals of nitrogen + Hybridized orbitals of oxygen
  = $3+4+3+3=13$.

Hence, there are 13 hybrid orbitals present in the case of${\mathrm{HNO}}_3$.