Ionization Energy

ionization energy:  the amount of energy that it takes to remove an electron from an atom.  Ionization energy is a measure of how strongly an element holds onto its electrons.

Elements that “want” electrons hold onto their own electrons more tightly, which means they have higher ionization energies.

· Atoms of elements farther to the right hold on more tightly, because they want to gain electrons, not lose them.  Elements to the left hold on less tightly, because they want to lose electrons anyway, so the only thing holding on to the electrons is the charge of the protons in the nucleus.

· Atoms of elements higher up hold on more tightly because they have fewer energy levels & sublevels to spread the electrons over, which makes each one more “valuable”.

· Noble gases and ions with the same electron configuration as a noble gas have the highest ionization energies, because they have exactly the number of electrons as they want.

· Helium has the highest ionization energy.  Francium has the lowest.