Question

Ionization enthalpy of nitrogen is more than oxygen because of:
a. Extra stability of half-filled orbital
b. More number of energy levels
c. Less number of valence electron
d. Smaller size

Answer 1

Hint : We must know that the ionization enthalpy depends upon the stability of the atom, higher the stability higher the ionization enthalpy.

Complete step by step solution :
Let’s start with what actually ionization enthalpy is? Well, Ionization enthalpy also known as ionization energy of elements can be defined as the amount of energy required by an isolated gaseous atom to lose an electron in its ground state. So, higher the ionization enthalpy for an atom also increases the stability of the atom.
We can also say that higher the stability of the isolated gaseous atom, higher the ionisation enthalpy of the atom.
When we compared the size of two atoms given to us oxygen has smaller size as compared with nitrogen. But the size is not the criteria for stability of an atom. The stability of an atom depends upon its valence orbital. If the valence orbital of an atom is fully filled it is the most stable after that comes the half-filled configuration.
Writing the electronic configuration of Nitrogen (N) and Oxygen (O) we get.
Nitrogen (N) atomic number 7: $1{s^2}2{s^2}2{p^3}$
Oxygen (O) atomic number 8: $1{s^2}2{s^2}2{p^4}$
In case of nitrogen (N) the 1s and 2s orbitals are completely filled whereas the p orbital is half filled. In case of oxygen (O) the 1s and 2s orbitals are completely filled and the 2p orbital is one more than the half-filled configuration.
As written above the half-filled configuration is just below the completely filled configuration in terms of stability so the stability of nitrogen atom is more as compared to oxygen and hence nitrogen ionization enthalpy is more.
So, we can conclude that the answer is A. Extra stability of half-filled orbital.

Note : We need to understand the concept of completely filled and half-filled orbits along with why these orbitals are more stable as compared to others. If atoms have half-filled and completely filled electrons. Therefore, it is more stable. This is because of the symmetrical distribution of electrons in orbitals. And the electrons in degenerate orbitals have a parallel spin and tend to exchange their position in the orbital.
We should also know the concept of electronic configurations.