# Lewis Acid and Base

1. May 25, 2016

### terryds

1. The problem statement, all variables and given/known data

In the reaction with NH3, is specy BH3 a Lewis base ?

2. Relevant equations
Lewis acid = electron acceptor
Lewis base = electron donor

3. The attempt at a solution

H electronegativity = 2.1
B electronegativity = 2.0
N electronegativity = 3
Since N-H bond is more electronegative than B-H bond, NH3 is more electronegative than BH3 which means that NH3 is more easily to accept electron. So, NH3 is Lewis acid, BH3 is Lewis base

Is it correct??
My book says that NH3 is the base with no reason, and I doubt that.

2. May 25, 2016

### sidt36

A good way to analyse the above problem would be to draw the Lewis structures.There is a reason it is named after G.N. Lewis!

3. May 25, 2016

### terryds

Alright,
Based on Lewis structure, NH3 have three pair of bonding electrons and one pair of free electrons while BF3 have three pair of bonding electrons.

and then? How to determine which one is base or acid ?

4. May 25, 2016

### sidt36

So the electron configuration is something like this

So i think this might help

5. May 25, 2016

### sidt36

My teacher Told me if it has an empty orbital ->Lewis acid
Otherwise its most likely ->Lewis base

6. May 25, 2016

### terryds

Thanks! I got it!

Last edited: May 25, 2016