Question

Sorry previous question was asked by mistake
this is the question
what is ionisation enthalpy

Answer 1

Ionization enthalpy is defined as the energy required to remove electron in the ground state of a gaseous isolated atom.

So it should be taken care that the atom is isolated meaning not in a combined state or bound with any other atom or molecule .

It should be in its ground state remember not in excited state.
Ionization enthalpy generally increases across a period and decreases down a group.