Download Covalent Bonds

Covalent Bonds
Covalent bonds - Elements sharing electrons
to form a bond.
Lewis Structures use Electron Dot Diagrams
to show how electrons are arranged in
molecules.
atoms
•
SHAR ING OF
ELECTRONS
TRA NSFER OF
ELECTRON
•
molecule
c o v alent bond
po.sitive
,o n
--
•
neg. ative
,o n
Strength of Bonds
Higher number of bonds between 2 atoms
corresponds to shorter bond lengths, and,
in general, to stronger bonds.
Drawing Lewis Structures
1. Arrange the atoms (Dot Diagrams).
a.
The LEAST electronegative atom is central
in the model (except Hydrogen).
i. Electronegativity increases left to right
and bottom to top.
b.
The central atom is often the 1st atom in the
formula.
c.
Carbon is ALWAYS central.
d.
Hydrogen/halogens are always terminal (on
end).
Drawing Lewis Structures
2. Form bonds:
a.
A dash (—) represents 1 pair of shared
electrons.
b.
A colon (:) equals a lone pair of electrons
(non-bonding electrons).
c.
Hydrogen can form only 1 bond since it only
needs 2 e- to be stable.
Drawing Lewis Structures
3. If central atom is not yet surrounded by 4
electron pairs or does not form an octet,
convert one or more of the lone pairs from
a terminal atom into double or triple bonds.
This will only happen with C, N, O, P, or S.
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Practice
Draw the Lewis structures for the following.
Cl2
HBr
H2 S
CCl4
PH3
Practice
Draw the Lewis structures for the following.
O2
CH4
N2
N2 O
H2 O