Question

Which one of the following is NOT a Lewis acid-base reaction?
1. ) Ca + S --> Ca2+ + S2-
2. ) BeF2 + 2 F- --> BeF42-
3. ) H+ + -O-H --> H-O-H
4. ) NH3 + BF3 --> H3N-BF3

i thought it was 1...but im not sure...but i know that 3 & 4 are definatly right.

Answer 1

In #2, the two F- ions are "donating" electron pairs to the Be atom in forming covalent bonds with Be. That makes F- a Lewis base and the Be atom a Lewis acid. In #1 there is a transfer of electrons from Ca to S in forming two ions. No covalent bonds are formed. Is that consistent with your answer?