The Lewis theory of acids and bases is a way to understand these substances that goes beyond older ideas.

1. Different Definitions:

   • Arrhenius: Says acids make $H^+$ ions and bases make $OH^-$ ions when mixed with water.
   • Bronsted-Lowry: Looks at acids as things that give away protons and bases as things that take in protons.
   • Lewis: Defines acids as things that grab electron pairs and bases as things that give away electron pairs.

2. Examples of Reactions:

   • In the Lewis theory, $BF_3$ (which is a Lewis acid) can react with $NH_3$ (which is a Lewis base) to create a stable compound. This shows that acid-base behavior is not just about exchanging protons.

3. Making Complexes:

   • The Lewis theory also helps us understand complex substances in coordination chemistry, like $Cu(NH_3)_4^{2+}$. Other theories don’t explain these well.

In short, the Lewis theory brings together different acid-base reactions by looking at how electrons interact. This makes it a useful tool in chemistry.