CHEMICAL BONDING
Chemical bonds
 forces holding particles together in a compound
 basis of chemical properties and reactions
Ionic Bond
 between metals and non-metals
 formation of ions is the tendency to achieve noble gas electronic
configuration
Cation – ion with positive charge (usually metals)
Anion – ion with negative charge (usually non-metals)
Formula unit – the smallest unit of an ionic compound
Naming ionic compounds –
1. Use elements name for the cation
2. Change the ending of the anions element name to IDE
Example:
NaCl – Sodium Chloride
Hydrogen – Hydride (H-1)
Oxygen – Oxide (O-2)
Phosphorus – Phosphide (P-3)
Ions arrange themselves into a Crystal Lattice (ions arranged in 3-D)
Covalent Bonds
 Formed between non-metals
 Electrons are shared by atoms
 Driving force is the tendency to gain stable octet
Example: Hydrogen gas
Example: Chlorine gas
Single bond – consists of just one shared pair of electrons
Example: Hydrogen Chloride
Example: Water
Double bond – consists of two shared pairs of electrons
Example: carbon dioxide (CO2)
Triple bond - consists of three shared pairs of electrons
Example: Nitrogen gas (N2) or Carbon monoxide (CO)
Covalent Molecules Cont'd
Diatomic molecules: 2 atoms covalently linked together
Diatomic gases: H2, Cl2, N2, O2, Br2, I2, F2
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Polyatomic molecules : 3 or more atoms joined together
Electronegativity and Covalent bonding
Electronegativity – measure of the tendency of an atom to
attract electrons towards itself when forming a covalent bond.
(values on P.T.)
Example 1
Diatomic gases have 2 identical atoms involved in bonding and so
their electronegativity values are exactly the same.
Example 2
Molecules with different types of atom have different
electronegativity values thus the sharing of electrons is not equal
POLARITY
Polarity – in a covalent bond, the shared electrons are more the
property of one atom than the other. Therefore one atom has a
slightly more negative charge than the other atom which has a
slightly more positive charge. These slight positive or negative
charges are referred to as partial charges and are represented
by the Greek letter delta.
Polarity can be determined by taking the difference in
electronegativity values.
Example 3
Note these partial charges are smaller than ionic compounds
(partially ionic).
The type of bond can be predicted by looking at the difference in
electronegativities of any two atoms that are linked covalently
Rule
Bond Type
Ionic bond
Polar Covalent bond
Non-Polar Covalent bond
Difference in Electronegativity Values
Greater than 1.7
Between 0.1 – 1.7
Less than 0.1 to 0
Determining types of bonds using electronegativity differences
Bond Type
Ionic bond
Polar Covalent bond
Non-Polar Covalent bond
Difference in Electronegativity Values
Greater than 1.7
Between 0.4 – 1.7
Less than 0.4 to 0
Naming Covalent Molecules is done using the Pre-fix method
# of atoms
Prefix
1
2
3
4
5
6
7
8
9
10
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca