1. Chemical Bonding
Covalent Bonding

2. How to play my game? Be respectful Be punctual
To give your VERY best in all the things that you do

3. Some queries.. Physical Properties of Ionic compounds Solubility
How it happens?
Electrical conductivity
Why do ionic compounds only conduct electricity in the molten or aqueous state?

4. Bonding and structure explains the properties of a substance!
Overview
Bonding
Ionic
Covalent
Metallic
Structure
Giant ionic
Simple molecular
Giant covalent
Giant Metallic
Example
Sodium chloride
Water
Diamond
Iron
Bonding and structure explains the properties of a substance!

5. Compare and Contrast

6. Ionic VS Covalent Ionic Bond Covalent Bond Similarities Differences
Octet Rule: Electronic configuration of a noble gas
(PS: Everybody wants to be noble!!)
Differences
Ionic Bond
Covalent Bond
Between positive ions of metals and negative ions of non-metals
Between non-metal atoms
Electrons are transferred
Electrons are shared

7. What to do??

8. Covalent Bonding

9. Covalent Bond: The Definition
A covalent bond is… a bond formed by the sharing of a pair of electrons.

10. More about COVALENT BONDING
Each atom acquires a stable octet structure
Electronic configuration of noble gas (Full shell) = Energetically stable
Formed between atoms of non-metals (but there are exceptions!)
“Spectrum” of bonds

11. Covalent Compounds of ELEMENTS
Hydrogen, H2 (Single covalent bond)

12. Covalent Compounds of ELEMENTS
Chlorine, Cl2 (Single covalent bond)

13. Covalent Compounds of ELEMENTS
Oxygen, O2 (Double covalent bond)

14. Covalent Compounds of ELEMENTS
Nitrogen, N2 (Triple covalent bond)

15. Covalent Compounds of COMPOUNDS
Draw the ‘dot-and-cross’ diagram for each of the following covalent compounds.
Hydrogen chloride
Ammonia

16. Covalent Compounds of COMPOUNDS
Water, H2O

17. Covalent Compounds of COMPOUNDS
Carbon dioxide, CO2

18. Simple Molecular Substances
Consists of small molecules, e.g. bromine

19. Simple Molecular Substances
Within the molecule
Atoms are held together by strong covalent bonds
Between molecules
Weak van der Waals’ forces (intermolecular forces)

20. Iodine, I2
Within each iodine molecule, the iodine atoms are held together by strong covalent bonds.
Between the iodine molecules, there are only weak van der Waals’ forces holding the molecules together.

21. Methane, CH4
In a molecule of methane, CH4, the four C–H covalent bonds are strong.
However, weak van der Waals’ forces between methane molecules hold them together loosely. Therefore, methane exists as a gas at room temperature and pressure.

22. Physical Properties Physical state Low M.P. & B.P.
Most substances are liquids or gases at room temperature.
Forces between molecules are weak, allowing molecules to move freely.
Low M.P. & B.P.
Little energy required to overcome the (weak) intermolecular forces
(Usually <200°C)

23. Melting & Boiling Points
Covalent substance
Melting point (C)
Boiling point (C)
Carbon dioxide
-56
-79
Chlorine
-101
-35
Hydrogen
-259
-253
Methane
-183
-161
Oxygen
-214
Water
100

24. Physical Properties Volatility Electrical conductivity Solubility
Low B.P. = Volatile
Evaporate easily (to give a smell)
Electrical conductivity
Do not conduct electricity. (Some exceptions, e.g. graphite)
No free-moving ions or electrons to conduct electricity
Solubility
Most molecular substances are insoluble in water, but dissolve in organic solvents. (Some exceptions, e.g. alcohol and sugar, hydrogen chloride)

25. So, what have you learnt? Covalent bonding
The definition of a covalent bond
A covalent bond is a bond formed by the sharing of a pair of electrons.
Formed between atoms of non-metals
(with exceptions!)
Atoms share electrons so that a octet structure can be obtained

26. Steps to take… Ionic or covalent?
Determine the electronic configuration of the atoms involved
How many electrons needed to achieve stable electronic structure?
Now, transfer/share the electrons!

27. So, what have you learnt? Simple molecular structure
Small covalent molecules
Strong covalent bonds between the atoms in the molecule
Weak intermolecular forces
5 physical properties

28. Giant Covalent Structures
Diamond
Graphite

29. Giant Covalent Structures
Diamond
Each carbon atom is joined to four other carbon atoms by strong covalent bonds. (Draw!)
Graphite
Each carbon atom is joined to three other carbon atoms by strong covalent bonds. (Draw!)