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Is the ammonium ion, NH4+ a Lewis Base or Acid?

Submitted by jtea816 on Sat, 09/20/2008 - 19:13

Hey guys! Just another question about Ammonium.

Is Ammonium an Lewis Base or Acid? I thought about it and I think it is neither.

Here is my thinking:
1.) Lewis Bases wants to donate an e- lone pair
2.) Lewis Acids wants to accept an e- lone pair.
3.) +NH4 has a full octet and does not have a lone e- pair so an e- lone pair is not available to be donated and it has a full octet, so this leads me to believe that +NH4 is neither a lewis acid or base.

is this correct? Thanks for your help!

your logic seems fine.  However, this may be a trick question.  Many textbooks and instructors have you look at all Bronsted-Lowry acids as automatically being Lewis acids because they donate a proton and the proton accepts an electron pair.