Why does Aluminium Fluoride have a higher b.p than Aluminium Chloride

Please can you explain it in terms for someone in high school?

Due to the differences in size (F- ions are much smaller than Cl- ions), attractive forces between AlF3 molecules are greater than between AlCl3 molecules. So it takes more energy to separate the molecules of AlF3 into a gas, making the boiling point higher.