## Valence/valency?

$sp, sp^{2}, sp^{3}, dsp^{3}, d^{2}sp^{3}$

StephanieDoan3B
Posts: 21
Joined: Fri Sep 29, 2017 7:07 am

### Valence/valency?

The book states, "It looks as though a carbon atom should have a valence of 2 and form two perpendicular bonds, but in fact it almost always has a valence of 4 (it is commonly “tetravalent”)..."

Valence is not the number of valence electrons because Nitrogen's valency is 3. Could someone please define the term "valence/valency"?

Golbarg Rahimi 3k
Posts: 26
Joined: Sat Jul 22, 2017 3:01 am

### Re: Valence/valency?

the valence number is the number of electrons located in the outer layer of the atom ( valence shell). These electrons can form bonds with other atoms, therefore they should not be paired. carbon has the electron configuration of (he)2s22p2 this means that there are 2 unpaired electrons in the outer shell. that is why carbon is expected to have a valence number of 2. However since this atom has empty orbitals, the electrons get promoted and form 4 unpaired electrons. now the atom could form 4 bonds so it has valence number of 4.