Lewis acids are electron pair acceptors.
Lewis bases are electron pair donors.
Look at H2O, for example.
  ..
H:O:
  ..
  H
This molecule has no "holes" to accept an electron. Would you expect this to be an acid or a base by Lewis standards?
Classify each as a lewis acid or lewis base...
A)H20
B)O2-
C)Cu2+
D)SO3
E)AlCl3
3 answers
I think it would be a base because like you said it has no space to accept any electrons. As, for the other compounds is this correct:
O2- is a lewis base
Cu2+ is a lewis base
AlCl3 is an acid
SO3 is an acid
????
O2- is a lewis base
Cu2+ is a lewis base
AlCl3 is an acid
SO3 is an acid
????
Apparently my response didn't post. I think Cu^+2 will be a Lewis acid. It wants to accept electrons to make that Cu(s).