Question

How does ionization energy decrease?

Answer 1

Ionization energy- It is the energy which is required to remove the electron from an atom.

Ionization energy decreases as

According to the modern periodic table, when we move downwards the group the ionization energy decreases. This happens because of two reasons one shielding effect and another is the atomic radius.

1. Increase in the Shielding Effect-The repulsion between the electrons in the inner shell and the valence electron is known as the shielding effect. These repulsions reduce the electrostatic attraction between the electrons and the nucleus, making the removal of the electrons easier.
2. Increase in the Atomic Radius- As the atomic number is increased, new electrons are added to the orbitals, therefore increasing the distances of electrons from the atomic nuclei. This factor, in addition to the shielding effect, reduces the net electrostatic force acting on the valence shell electrons, thereby reducing their ionizing energy.

Thus, the ionization energy decreases as you move down the group in the periodic table due to the increase in the shielding effect and due to the increase in the atomic radius.