The boiling points of the aluminium halides

Question

I would like to ask why the boiling points of the aluminium halides are in the order:

AlF3 >> AlI3 > AlBr3 > AlCl3

Answer 1

最愛解答

你係某某論壇都問過呢個問題,我係埋呢度答多一次

Al的electronegativity是1.5,Cl是3

故bonding是partially ionic or partially covalent-->AlCl3 boiling point最低

F的EN是4.0,delta EN是4-1.5=2.5-->polarizability最強,故boiling point最強

AlI3大舊個AlBr3,分子size大D,van der Waals' forces大D

另類解法:

Since F- is not so polarizable, AlF3 is ionic & has the hightest boiling point(strong electostatic forces)

As the other halide ions are polarizable,AlCl3,AlBr3&AlI3 possess high covalent character & are similar to simple molecular substances. As the strength of can der Waals' forces increases with the molecular sizes, the strengths of van der Waals' forces are in the order of AlI3 > AlBr3 > AlCl3

資料來源： 自己+少少書本上