covalent bond
DESCRIPTION
TRANSCRIPT
Covalent Bonding
Chemical Bonding
…atoms share electrons to get a full valence shell
Covalent Bonds
C 2s2 2p2 (4 v.e–)
F 2s2 2p5 (7 v.e–)
both need 8 valence electrons for a full outer shell(octet rule)
1s2
1s2
Covalent bonding
F F
• Fluorine has seven valence electrons• A second F atom also has seven• By sharing electrons• Both end with full orbitals (stable octets)
8 Valence electrons
8 Valence electrons
Covalent Bonding
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-
n = 1
O[He]2s22p4
n = 2
+
-
----
-
-
O2
Sharing of electrons to achieve a stable octet (8 electrons in valence shell).
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O[He]2s22p4
Covalent/Molecular Compound
Silicon dioxide, SiO2, is a molecular compound. It is also a mineral called quartz (left).Quartz is found in nearly every type of rock. Most sand grains (center) are bits of quartz.Glass is made from sand.
A compound containing atoms of two or more elements that are bonded together by sharing electrons.
Covalent Bonding - True Molecules
Types of Bonds
Diatomic Molecule
Ammonia
Nitrogen
Water
Covalent vs. Ionic
Covalent
Transferelectrons
(ions formed)
+ / -
BetweenMetal andNonmetal
StrongBonds
(high melting point)
Shareelectrons
(polar vs. nonpolar)
BetweenTwo
Nonmetals
Weak Bonds
(low melting point)
Alike Different
Electronsare
involved
ChemicalBonds
Ionic
Different
Topic Topic
Lewis Structure
Lewis structure: a model of a covalent molecule thatshows all of the valence electrons
1. Two shared electrons make a single covalent bond,
four make a double bond, etc.
2. unshared pairs: pairs of un-bonded valence electrons
3. Each atom needs a full outer shell, i.e., 8 electrons. Exception: H needs 2 electrons
Lewis Structure
carbon tetrafluoride (CF4)
o
Co
o
o x
xx
x
x x
F x
o
Co
o
ox
xx
x
x x
F x
x x
x
x
x x
F x
x
xx
x
x
F x
x
x
xx
x x
F x
xCx
xx
x
x x
F
x x
x
x x
F x
x
xx
x F x
x
xx
x x
F x
x
covalent compounds = molecular compounds(have lower melting points than do ionic compounds)
Lewis Structure
o
Co
o o
x
Ho
Co
o oH x
x
H
xH
x H CH
H
H
H
x
xxx
x x
I xo
No
o o
o o
No
o ox
xxx
x x
I x
x x
xx
x x
I x
xxx
x x I x
x
o o
Nx
xxx
x x
I
x xx
x x
I x
xx
x x I x
x
o
o
Co
o o x
xxx
xO x
x
xxx
xO x
x
xxx
xO x
o
Co
o o O = C = O
x x
x x x x
x x
methane (CH4)
carbon dioxide (CO2)
nitrogen triiodide (NI3)