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Covalent Bonding
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Takes place between two non-metals
Electrons are shared by both nuclei to help
each attain 8 valence electrons
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If the electrons are shared equally it is a nonpolar covalent bond
If the electrons are not shared equally it is a polar
covalent bond
A molecule is formed when two or more
atoms bond covalently
Covalent Bond Video (25 sec)
Ionic and Covalent (2 min)
2
Properties of Covalent
Compounds
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Low melting points.
Many are liquids and gases at room
temperature.
Polar covalent molecules dissolve in water.
Nonconductors of electricity.
Lewis Structures
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Using an atoms dot diagram we can predict
how different atoms will bond covalently to
form molecules
Each bond between atoms requires each
atom to share one electron with the other
atom.
Example:
F
F
F-F
Dot Diagram Steps
1. Draw out atoms with
valence electrons (dot
structures)
2. Connect 2 e- to share until
all atoms have full shells
3. Redraw with connected
electrons as the bond
4. Redraw any lone pairs of
electrons not involved with
bonding
NH3
H
H
N
H
H
H N H
5
Double and Triple bonds
Sometimes more than one pair of electrons are
shared to meet the octet rule
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Double Bonds= 2 pairs of electrons shared
between two atoms
Triple Bonds= 3 pairs of electrons shared
between two atoms
Covalent Lewis Structures: Multiple Bonds
When two electron pairs are shared between
two atoms, the resulting bond is a double
bond.
 these bonds are shorter and stronger than
single bonds
Consider oxygen gas:
7
Covalent Lewis Structures: Multiple Bonds
When three electron pairs are shared between
two atoms, the resulting bond is a triple bond
 these bonds are shorter and stronger than
double or single bonds
Consider nitrogen gas:
8
Some Clues for Drawing Dot
Diagrams
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Put the single atom in the middle of the dot
diagram (the one that will have the most
bonds)
Hydrogen is never in the middle of the dot
diagram
When redrawing, we use
dashes to represent 2
shared electrons
Remember to redraw the
nonbonding electrons
H
H
N
H
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Practice Drawing
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Draw dot diagrams for the following:
CH4
PCl3
SH2
CO2
COH2
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Exceptions to the Octet Rule
The Lewis structure for NO (having odd number
of electrons)
 The Lewis structure that deals with boron (B):
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boron shares 3 electrons to form three single bonds
Beryllium (Be) shares 2 electrons to form two single
bonds
The Lewis structures of SF6 and PCl5 (for elements in
Period 3 or greater)
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Lewis Structures
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some common bonding patterns
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C = 4 bonds & 0 lone pairs
Different bonding combinations:
 4 single bonds
 2 double bonds
 1 single + 1 triple bond
 2 single + 1 double bond
N = 3 bonds & 1 lone pair
O = 2 bonds & 2 lone pairs
H and halogen = 1 bond
Be = 2 bonds & 0 lone pairs
B = 3 bonds & 0 lone pairs
B
C
N
O
F
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Naming Covalent Bonds
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Write names of both elements
Add -ide to the last name
Add prefixes at beginning of each word to
indicate how many of each element.
Exception- do not use mono in front of the
first element
N2O5
Dinitrogen Pentaoxide
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Covalent Bonding Prefixes
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
(mono-)
ditritetrapentahexaheptaoctanonadeca14
Practice Naming
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Name the following:
CH4
PCl3
SH2
CO2
C 2H 2
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Diatomic Elements
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elements that always occur in pairs
name these using the element name
H2, N2, O2, F2, Cl2, Br2, I2 (need to memorize all 7)
Common Covalent Compounds
 H 2O
 NH3
 CH4
Water
Ammonia
Methane
Also need to be
memorized
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Naming Compounds Review
What type of compound is it?
Covalent: Small electronegativity difference (N/N)
Electrons are shared
1. Add -ide to second element
2. Add prefixes to beginning of words (except NO mono to
start a name)
Ionic: Large electronegativity difference (M/N)
Electrons are gained/lost
Is there a choice of charges?
Metal has a known constant charge:
Cation is element name, anion is element name with –ide on end
or polyatomic ion
Metal can have multiple charges
Cation is element name , use roman numerals to indicate
charge on metal, anion is element name with –ide on end or
polyatomic ion
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Acid Nomenclature
How to identify an acid:
The formula of an acid starts with “H” (for now)
HCl
hydrochloric acid
How to identify an acid:
The formula of an acid starts with “H” (for now)
HNO3
nitric acid
How to identify an acid:
The formula of an acid starts with “H” (for now)
H3PO4
phosphoric acid
Two types of acids:
1. Binary Acids
(Two elements, one of
which is hydrogen)
HCl
HBr
H2S
2. Oxyacids
(contain oxygen, usually a
polyatomic ion bonded to
hydrogen)
H2SO4
HClO3
HClO4
If it is a binary acid:
Prefix = Hydroroot = second element’s name
Suffix = -ic acid
HCl = hydro- chlor -ic acid→ hydrochloric acid
HBr= hydro- brom -ic acid →hydrobromic acid
H2S = hydro – sulfur – ic acid →hydrosulfuric acid
If it is an oxyacid
1.
2.
3.
Prefix = none
root = anion (polyatomic name)
Suffix =depends! + acid
If anion ends in –ate replace with –ic acid
If anion ends in –ite replace with –ous acid
Example: HNO₃
Example: HNO₂
Since NO₃⁻ = Nitrate
Since NO₂⁻ = Nitrite
HNO₃ = Nitric Acid
HNO₂ = Nitrous acid
*Sulfate/ite root goes to sulfur (sulfuric and
sulfurous acid). Same is true for phosphate
For Example
Acid’s Formula
If the anion (-) name
is…
The acid formed from
this anion is named…
HCl
chloride
hydrochloric acid
HClO
hypochlorite
hypochlorous acid
HClO2
chlorite
chlorous acid
HClO3
chlorate
chloric acid
HClO4
perchlorate
perchloric acid
Examples
1.
2.
3.
4.
5.
6.
HNO2
H2SO3
H3PO4
HNO3
HCl
H2SO4
Examples- answers
1.
2.
3.
4.
5.
6.
nitrous acid
sulfurous acid
phosphoric acid
nitric acid
hydrochloric acid
sulfuric acid
Try on your own
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1. HCl
2. HBr
3. H₂SO₄
4. H₂S
5. H₂CO₃
6. HC₂H₃O₂
7. H₃PO₄
8. H₃P
9. H₂CrO₄
10. H₂Cr
Answers
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1. HCl- hydrochloric acid
2. HBr- hydrobromic acid
3. H₂SO₄- sulfuric acid
4. H₂S- hydrosulfuric acid
5. H₂CO₃- carbonic acid
6. HC₂H₃O₂- acetic acid
7. H₃PO₄- phosphoric acid
8. H₃P- hydrophosphoric acid
9. H₂CrO₄- chromic acid
10. H₂Cr- hydrochromic acid
Try writing the formulas:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Sulfuric acid
Nitric acid
Hydrochloric acid
Acetic acid
Hydrofluoric acid
Phosphorous acid
Carbonic acid
Nitrous acid
Phosphoric acid
Hydrosulfuric acid
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
H₂SO₄
HNO₃
HCl
CH₃COOH
HF
H₃PO₃
H₂CO₃
HNO₂
H₃PO₄
H₂S