# Lecture Notes For Bonding and Lewis Dot Structures

### Covalent Bonding

Another aid:

S = N - A

S = total # e-shared
N = total # e- needed to complete octets
A = total # e- available to molecule (sum of valence e- adjusted for any ionic charges

S = N - A
S = [1(2) + 2(8)] - [1 + 6 + 7]
S = [18 - 14]
S = 4 shared e- or 2 covalent bonds
S = N - A
S = [3(2) + 2(8)] - [3(1) + 5 + 6]
S = [22 - 14]
S = 8 shared e- or 4 covalent bonds

### Multiple Bonds

S = N - A
S = [1(2) + 3(8)] - [1 + 2(6) + 5]
S = [26 - 18]
S = 8 shared e- or 4 covalent bonds

Covalence Numbers:

The number of covalent bonds in which an atom participates when it has no formal charge.

 Atom Covalence Number # Lone Pairs H 1 0 C 4 0 N 3 1 O 2 2 Halogens 1 3 B* 3 0

Formal charges will result when an atom in a molecule does not have its optimum covalence number.

*Boron does not obey the octet rule. In neutral compounds, it possesses only 6 electrons.
 Atom # Covalent Bonds Covalence # F.C. ammonium ion H 1 1 0 N 4 3 +1 tetrafluoroborate ion F 1 1 0 B 4 3 -1

Nitrogen needs to own 5 valence electrons for neutrality (each lone pair electron belongs to N and one in each covalent bond will belong to N. In this example, N owns only 4 valence electrons so F.C.= +1 Boron needs to own 3 valence electrons for neutrality. In this example, B owns 4 valence electrons so F.C.= -1.