Question

How does atomic number affect ionization energy?

Answer 1

Ionization energy is the minimum amount of energy required to remove the most loosely bound electron from an isolated atom. The loss of electrons usually happens in the ground state of the chemical species. It is a measure of strength (attractive forces) by which an electron is held in a place. It is an endothermic process and also termed as ionization potential.

Complete answer:
As we already know ionization energy is the least amount of energy required to remove form an atom.
On moving the group the atomic size increases along with the atomic number also increases, the number of inner shells i.e., the number of inner electrons also increases as a result, the screening effect increases, which reduces the force of attraction and valence electrons and therefore ionization energy decreases.
On moving from left to right along a period. The atomic number decrees and atomic radii with natural or decrease in screening effect which increase the force of attraction towards the nucleus and hence electrons are difficult to remove. So a large amount of ionization energy will require to remove electrons. So across the period of ionization energy increases with increase in atomic number.
So we can conclude that ionization energy and atomic number show an inverse relation.
With increase in atomic number ionization energy decrease with decrease in atomic number ionization energy increase.
Ionization energy gives us an idea of the reactivity of chemical compounds. It can be used to determine the strength of chemical bonds. It is measured in electron volts or kj/mol.
Two factors affect ionization energy are:
Force of attraction between electrons and the nucleus
The force of repulsion between electrons.

Note: A general trend is seen of small decrease in ionization energy when we go from the electron being removed from an s- subshell to being removed from an p- subshell. Because the p-shell has slightly higher energy, so less energy is required to remove the electron.