Question

Why is the ionization energy of group 15 elements higher than that of group 14 elements?

Answer 1

15 grup element have high i.p than 14 grup element as atomic size decrease from left to right and then the atom become small it become difficult to withdraw electron from it and hence require highr energy  for removal of electron

Answer 2

Explanation: Ionization energy is the energy required to remove an electron from the valence shell of an isolated gaseous atom.

In group 15, the valence electrons are 5 which gives the electronic configuration $ns^2np^3$. Here, the p-orbital is half filled and is in the most stable configuration. Therefore, removing an electron from this orbital will not be favorable. Hence, to remove an electron it requires more energy.

Whereas in group 14, the valence electrons are 4 and the electronic configuration is $ns^2np^2$. Here, the orbital is not in its stable configuration. hence, it can remove an electron easily.