Chemical bonding

1. Chemical Bonding Chemical Bonding
Presented by:Presented by:
Gulfam HussainGulfam Hussain

2. Chemical BondingChemical Bonding
►Chemical compounds are formed by the Chemical compounds are formed by the
joining of two or more atoms.joining of two or more atoms.
►
►A stable compound occurs when the total A stable compound occurs when the total
energy of the combination has lower energy energy of the combination has lower energy
than the separated atoms. than the separated atoms.

3. The two extreme cases of chemical The two extreme cases of chemical
bonds are: bonds are:
Covalent bond: bond in Covalent bond: bond in
which one or more pairs of which one or more pairs of
electrons are shared by two electrons are shared by two
atoms. atoms.
Ionic bond: bond in which Ionic bond: bond in which
one or more electrons from one or more electrons from
one atom are removed and one atom are removed and
attached to another atom.attached to another atom.

4. Other Types of Bonds
Metallic Bonds:
In metals all atoms loses their valence
electrons which form electronic cloud , which
attracts the nucleus of neighboring atoms.
Hydrogen Bonding:
Electrostatic force of attraction between highly
electronegative atom and partially positive
hydrogen atom e.g water.

5. Ionic Bond
An ionic bond  is a type of chemical 
bond formed through an electrostatic attraction 
between two oppositely charged ions. Ionic 
bonds are formed between a cat ion, which is 
usually a metal, and an anion, which is usually 
a nonmetal.
Example:
NaCl forms ionic bond.

6. How are Ionic Bonds Formed?How are Ionic Bonds Formed?

Elements from opposite ends of the Elements from opposite ends of the
periodic table will generally form ionic periodic table will generally form ionic
bonds. bonds.

7. Properties of Ionic CompoundsProperties of Ionic Compounds
Crystalline solidsCrystalline solids
High melting and boiling points High melting and boiling points
Conduct electricity when melted Conduct electricity when melted
Many soluble in water but not in nonpolar Many soluble in water but not in nonpolar
liquid liquid

8. Covalent BondsCovalent Bonds
bond in which one or more pairs of bond in which one or more pairs of
electrons are shared by two atoms.electrons are shared by two atoms.
The atoms in covalent bonds do not The atoms in covalent bonds do not
lose or gain electrons, instead lose or gain electrons, instead
They share pairs of electrons to They share pairs of electrons to
achieve stability, often by filling achieve stability, often by filling
their outer energy levels to their outer energy levels to
achieve an octet.achieve an octet.
Example: N2 forms covalent bond.Example: N2 forms covalent bond.

9. How are Covalent Bonds Formed?
Elements which are close together in
electronegativity tend to form covalent bonds
and can exist as stable free molecules.
Carbon dioxide is a common example.


10. First Subtype of Covalent First Subtype of Covalent
BondingBonding
Nonpolar bondNonpolar bond
Example: HExample: H
2
Because both atoms in the HBecause both atoms in the H
2 molecule molecule
have an equal attraction (or affinity) for have an equal attraction (or affinity) for
electrons, the bonding electrons are electrons, the bonding electrons are
equally shared by the two atoms, and a equally shared by the two atoms, and a
nonpolar covalent bond is formed. nonpolar covalent bond is formed.

11. Second Subtype of Covalent Second Subtype of Covalent
BondingBonding
•Polar Bond
•formed when electrons are unequally
shared between two atoms
•Example: the hydrogen-oxygen bond in
the water molecule.

12. Properties of Covalent Properties of Covalent
CompoundsCompounds
•Gases, liquids, or solids
•Low melting and boiling points
•Poor electrical conductors in all phases
•Many soluble in non polar liquids but not in
water
•Are brittle
•When 2 atoms bond covalently the
resulting particle is a molecule

13. Coordinate Covalent Coordinate Covalent
BondsBonds
Covalent bonds in which both of the electrons Covalent bonds in which both of the electrons
in the shared pair come from the same atomin the shared pair come from the same atom
Covalent bonds don’t lose or gain electronsCovalent bonds don’t lose or gain electrons
Electrons are not shared equallyElectrons are not shared equally
Example:Example:
The bond between NH3 and BF3 is The bond between NH3 and BF3 is Coordinate Coordinate
Covalent Bonds Covalent Bonds

14. What Have You Learned?What Have You Learned?
What are the two extreme cases What are the two extreme cases
of bonds?of bonds?
Do covalent bonds lose or gain Do covalent bonds lose or gain
electrons? (Yes or No).electrons? (Yes or No).
Why do atoms bond?Why do atoms bond?

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