What kind of bond is in #"AlF"_3#?
1 Answer
Ultimately, I would say it is ionic (and about as ionic as in
If you consider the electronegativity difference:
#EN_F - EN_(Al) = 4.0 - 1.61 = 2.4# ,which suggests the bond is ionic, since the usual cutoff is
#DeltaEN = 2.0# . But this isn't the only way to look at it.
Another way to look at it is to look at the percent ionic character, proposed empirically by Linus Pauling:
#bb(%"Ionic Character" = (1 - e^(-(DeltaEN//2)^2)) xx 100%)# ,where
#DeltaEN# is the difference in the two electronegativities.
Physically, it means the extent to which electrons are hogged by one atom (100% ionic character) rather than shared between the atoms (0% ionic character).
So:
#%"Ionic Character" ("Al"-"F")#
#= (1 - e^(-(2.4//2)^2)) xx 100% = bbul(76.3%)#
Now, we could compare that to HCl (which we consider polar covalent) and CsCl (which we consider ionic):
#%"Ionic Character" ("H"-"Cl")#
#= (1 - e^(-((3.16 - 2.2)//2)^2)) xx 100% = ul(20.6%)#
#%"Ionic Character" ("Cs"-"Cl")#
#= (1 - e^(-((3.16 - 0.79)//2)^2)) xx 100% = ul(75.4%)#
So, yeah, the