What is meant by ionisation energy

What is meant by ionization energy?

Ionization energy or ionization potential is the minimum amount of energy required to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule. The amount of energy required to remove an electron from an isolated atom or molecule.

Example of ionization energy

1) Ionization energies measure the tendency of a neutral atom to resist the loss of electrons. It takes a considerable amount of energy, for example, to remove an electron from a neutral fluorine atom to form a positively charged ion.

2) Ionization: Changing Atoms Into Charged Ions

Some examples that you may be familiar with include: When sodium and chlorine combine to make salt, the sodium atom gives up an electron resulting in a positive charge while chlorine gets the electron and becomes negatively charged as a result.

the answer for sodium is 0.186

the answer for rubidium is 0.251

i just learnt this recently but i need to look through my notes again