The minimum energy to ionize an atom is the energy required to

Options

A. add on electron to the gaseous state of atom
B. excite the atom form its ground state to its first excited state
C. remove one outermst electron from the gaseous state of atom
D. remove one innermost electron from the gaseous state of atom

Answer

C

Explanation

The minimum energy required to ionised an tomi is equal to the energy to excite an electron an electron in the atom from its ionisation level corresponding to `n=oo` . If the atom is given an amount of energy equal to the ionisation energy, the electron is just able to become a free electron and the atom is about to be ionised.
When this occurs, one outermost electron from the atom is just to be removed from the atom. Much higher energy is necessary to free an innermost electron from the atom because this will occur only after the outermost electrons are all removed.