Question

define ionisation enthalpy. Explain the factor which affect its value

Answer 1

The ionization energy (Ei) is qualitatively defined as the amount of energyrequired to remove the most loosely bound electron, the valence electron, of an isolated gaseous atom to form a cation. It is quantitatively expressed in symbols as X + energy → X+ + e−...
Basically there are five factors which can affect the Ionization energy like size of an atom,The effective nuclear charge,Shielding effect,Penetration effect and electronic configuration of an atom.All these factors related to the number of electrones in the valence shell and between the valence shell and nucleus.

Answer 2

the amount of energy required to remove an electron from a neutral isolated gaseous atom and convert it into a positively charged ion
atomic radii affects its value