Covalent Bonding

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DEFINITION
•Sharing of electrons
•Non-metal + non-metal
Single bond (H2O, CH4)
Double bond (O2, CO2)
Triple bond (N2)
•Properties of Covalent Compounds
Are usually gas, liquid or solid with low
melting points ( < 300°C)

Covalent Bond
POLAR NON POLAR

COVALENT COVALENT
• Exist between • Exist between
dissimilar atom similar atom
Example: Example:
H2O O2
CH4 Cl2
H2

What is a covalent bond?
Non-metal elements usually just need one or two electrons
to fill their outer shells. So how do they form a bond?
incomplete
Cl outer shells Cl
The two non-metal atoms cannot form a bond by transferring

electrons from one to another. Instead, they share electrons.
Each atom now
Cl Cl has a full, stable
outer shell.
The shared electrons join the atoms together. This is called

a covalent bond.

Types of Covalent Bonding
• SINGLE COVALENT BOND

It is formed when a pair of electrons between two
atoms is shared. (short line)
• DOUBLE COVALENT BOND
It is formed when two pairs of electrons between two
atoms is shared. (double short line)
• TRIPLE COVALENT BOND
It is formed when three pairs of electrons between
two atoms is shared. (triple short line)

How is a covalent bond drawn?
A covalent bond consists of a shared pair of electrons.
Cl Cl
covalent bond
Only outer shells of electrons are involved in bonding, so the
inner shells do not always have to be included in diagrams.
Two common ways to represent a covalent bond are:
simplified Cl–Cl
dot and solid
cross
diagram
Cl Cl line Cl – Cl
Can compounds contain covalent bonds?
Covalent bonding can also occur between atoms of different

non-metals to create molecules of covalent compounds.
These covalent bonds can be single, double or triple.
How is a covalent bond formed in hydrogen chloride (HCl,
also represented as H–Cl)?
H Cl H Cl
Hydrogen and chlorine both need one more electron to fill

outer shells. By sharing one electron each, they both have
a stable outer shell and a covalent bond is formed.
Covalent bonding in carbon dioxide
How do carbon and oxygen atoms form covalent bonds in
a molecule of carbon dioxide?
element C O
electron
configuration (2.4) (2.6)
O C O
electrons
needed 4 2
ratio of
atoms 1 2
double bonds
CO2 or O C O
A double bond is when two pairs of electrons are shared.
In carbon dioxide there are two double bonds
– one between each oxygen atom and the carbon atom.
What are giant covalent structures?
In some substances, such as sand, diamond and graphite,
millions of atoms are joined together by covalent bonds.
The covalent bonds in these substances do not form

molecules but vast networks of atoms called giant covalent
structures.
All the bonds are covalent, so giant covalent structures have
very high melting and boiling points, and are usually hard.
Writing Lewis Dot Formulas
• The Lewis electron-dot formula of a

covalent compound is a simple two-
dimensional representation of the
positions of electrons in a molecule.
– Bonding electron pairs are indicated by either
two dots or a dash.
– In addition, these formulas show the positions of
lone pairs of electrons.

• The following rules allow you to write

electron-dot formulas even when the
central atom does not follow the octet rule.
– To illustrate, we will draw the structure of PCl3,

phosphorus trichloride.
PCl 3
• Step 1: Total all valence electrons in the

molecular formula. That is, total the group
numbers of all the atoms in the formula.
PCl 3 26 e- total
5 e- (7 e-) x 3
– For a polyatomic anion, add the number of
negative charges to this total.
– For a polyatomic cation, subtract the number of
positive charges from this total.

• Step 2: Arrange the atoms radially, with the

least electronegative atom in the center. Place
one pair of electrons between the central atom
and each peripheral atom.
Cl Cl
P
Cl
• Step 3: Distribute the remaining electrons

to the peripheral atoms to satisfy the octet
rule. :
:
:Cl: :Cl :
P
:Cl :
:

• Step 4: Distribute any remaining electrons to the

central atom. If there are fewer than eight
electrons on the central atom, a multiple bond
may be necessary.
:
:
:Cl: : :Cl :
P
:Cl :
:

• Try drawing Lewis dot formulas for the

following covalent compound.
SCl2 20 e- total
16 e- left
4 e- left
: :
: :
: Cl S : :
Cl :

METALLIC BOND
• Is the force of attraction that holds metals
together
• Consists of the attraction of the free-
floating valence electrons for the positively
charged metal ions
• Explains many physical properties of
metals
Metals are good conductors of electricity
Metals are ductile
Metals are malleable

QUIZ
•Chemical
Nomenclature of
Inorganic
Compounds and
Chemical Equations
• Write the symbol of the
positive particle or cation first
before the symbol of the
negative particle or anion.
• Example: Na+ Al3+
O2- F-

• Criss-cross the valence
numbers, disregarding the
sign, so that the charge of the
cation becomes the subscript
of the anion and the charge of
the anion becomes the
subscript of the cation.
Example:
•Na + F
+ - K -
+ O2-
• Na1 F1 K2O1

If the subscript is 1,
it is no longer
written.
•Ex.: NaF K2O
If the subscript of both cation
and anion are the same, omit
writing the subscripts.
• Example: Mg2+ + S 2-
MgS

Reduce the subscript to the
simplest whole number
ratio.
• Example: W 6+
+ O2-
• W2O6 ------- WO3

When the polyatomic ion needs a
subscript, enclose it first with a
parenthesis. If the original
polyatomic ion already contains a
parenthesis, use a bracket.
Al3+ + Cr2O72- B3+ + Fe(CN)64-

Al2(Cr2O7)3 B4[Fe(CN)6]3
Naming Chemical Formulas
• Rules for naming inorganic

compounds
• Binary compounds
containing a metal and a
non-metal
• Give the name of the cation
first followed by the anion
• Transition metals
• Old/traditional system
• FeBr2 – ferrous bromide
• FeBr3 – ferric bromide
Stock system
• FeBr2 – iron (II) bromide
• FeBr3 – iron (III) bromide
Ion Stock System Old System
Fe2+ Iron (II) Ferrous
Fe3+ Iron (III) Ferric
Cu+ Copper (I) Cuprous
Cu2+ Copper (II) Cupric
Sn2+ Tin (II) Stannous
Sn4+ Tin (IV) Stannic
Pb2+ Lead (II) Plumbous
Pb4+ Lead (IV) Plumbic
Hg+ Mercury (I`) Mercurous
Hg2+ Mercury (II) Mercuric
Au+ Gold (I) Aurous
Au2+ Gold (III) Auric

Binary compounds containing two non-
metals
• Use prefixes to indicate the

numbers of atoms present
• Mono is never used in the first
element
NO2 – nitrogen dioxide
P2O5 – diphosphorus pentaoxide

Binary acids
• Non-oxygen acids
• Use the prefix hydro followed
by the anion and the word acid
added at the end
HCl – hydrochloric acid
• H2S – hydrosulfuric acid

Ternary compounds
• Compounds containing
more than two elements
• Give first the name of the
cation followed by the anion
K2SO4 – potassium sulfate
NH4NO3 – ammonium nitrate
Ternary acids
• Oxyacids
• -ite (ous ending)
• -ate (ic ending)
HNO2 – nitrous acid (hydrogen + nitrite)
HNO3 – nitric acid (hydrogen + nitrate)
HClO2 – chlorous acid (hydrogen +
chlorite)
HClO3 – chloric acid (hydrogen +
chlorate)

Covalent Bonding

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POLAR NON POLAR

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The two non-metal atoms cannot form a bond by transferring

The shared electrons join the atoms together. This is called

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• SINGLE COVALENT BOND

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A covalent bond consists of a shared pair of electrons.

Covalent bonding can also occur between atoms of different

Hydrogen and chlorine both need one more electron to fill

The covalent bonds in these substances do not form

• The Lewis electron-dot formula of a

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• The following rules allow you to write

– To illustrate, we will draw the structure of PCl3,

• Step 1: Total all valence electrons in the

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• Step 2: Arrange the atoms radially, with the

• Step 3: Distribute the remaining electrons

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• Step 4: Distribute any remaining electrons to the

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• Try drawing Lewis dot formulas for the

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• W2O6 ------- WO3

Al3+ + Cr2O72- B3+ + Fe(CN)64-

• Rules for naming inorganic

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• Use prefixes to indicate the

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