Chemical Bonding
- Formation of ions
- Formation of ionic bonds & covalent bonds
- Properties of ionic & covalent compounds
- Structure of simple, molecular & giant molecular structures

Noble Gas Structure
- Eg. He, Ne, Ar, Kr, Xe
- Each atom has 8 valence electrons (except for He)
- Single atoms
- Do not form compounds
- Described as unreactive
- Stable due to fully filled outer shells

The Octet Rule
- All atoms without a fully filled outer shell is unstable
- Unstable atom would try to gain stability by surrounding itself with an octet (8) of electrons
- Octet Rule

Helium (He)
- 2 outer electrons
- Stable atom because outer shell is fully filled
- Duplet Rule

Valency
- Number of electrons needed to fill up the outer shell
- Number of electrons in excess to the atom, stopping the atom from having a fully filled outer shell

Formation of Ions
- Charged particle formed from an atom/group of atoms by the loss/gain of electrons
- Metals formed positively charged ions called Cations.
- Non-metals formed negatively charged ions called Anions.

Formation of Positive Ions
- Formed by loss of electrons
- Metals tend to form positive ions because most metal atoms have less than 4 electrons in the outer shell. Hence it is more likely to lose the few electrons than to gain many more to achieve octet structure.

Formation of Negative Ions
- Formed by the gain of electrons
- Non-metals tend to form negative ions because most non-metals have more than 4 electrons in the outer shell. Hence, it is more likely for the atoms to gain a few more electrons to complete the octet than to transfer their outer electrons to other atoms.

Ions
- Positive and negative ions can be formed by a group of atoms, known as polyatomic ions

Ionic Bonds
- Formed between metals and non-metals
- Involves the formation of both positively charged ions (cations) and negatively charged ions (anions)
- Involves the transfer of electrons from one atom to another
- All metal atoms are known as electron donors and all non-metal atoms are known as electron receivers.

Ionic Compounds
- Made up of oppositely charged ions, NOT molecules
- Oppositely charged ions are arranged together in a giant ionic structure
- Lattice structure/Crystal lattice
- THree-dimensional network of atoms/ions which are packed together in a regular pattern
- Held together very tightly because oppositely charged ions attract one another strongly
- High melting and boiling points
- In order for the ionic solid to melt, a very large amount of heat energy is needed to break up the strong ionic bonds
- All ionic compounds are solids at room temperature
- Substances with low melting and boiling points are known as volatile
- Ionic compounds - Non-volatile
- Solubility:
       - Most ionic compounds can dissolve in water
       - Water molecules can separate the positive ions from the negative ions
       - Ionic compounds do not dissolve in organic solvents
- Able to conduct electricity in the molten (liquid) state) and as an aqueous solution
- Moving ions acts as charges carriers to conduct electricity

Covalent Bonds
- Two non-metals reacting with each other
- Bond formed by the sharing of electrons is called Covalent Bond
- In the case of ionic bonding, atoms would achieve stable duplet/octet structure by donating or receiving electrons. All non-metal atoms have a choice of whether to undergo ionic or covalent bonding depending on the nature of the other reactants.

Molecules of Compounds
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