O Level Chemical Bonding: Covalent, Ionic & Metallic Bonding

The complete repository for the O Level topic of Chemical Bonding

SKIM OVER CHEMICAL BONDING

Noble gas

Noble Gas Electronic Configuration

Chemical bonding occurs for atoms to obtain the same number of valence electrons as a noble gas.

Helium has 2 valence electrons (duplet).
All other noble gases have 8 valence electrons (octet).

Donating and receiving electrons in the formation of ions

Ion

A positively or negatively charged particle when an atom loses or gains electrons respectively, to obtain the noble gas electronic configuration.

Metallic elements lose electrons to form positively charged cations. Non-metallic elements lose electrons to form negatively charged anions.

Chemical bonding between atoms in a neutral molecule

Molecule

An electrically neutral particle made up of two or more atoms joined together by covalent bonds.

Atoms combine chemically by sharing electrons to form molecules.

Overlap of orbitals to form covalent bond

Covalent Bond

Sharing of valence electrons to obtain the noble gas electronic configuration.

Non-metals form covalent bond with each other in neutral molecules or charged polyatomic ions.

Opposite charges attract

Ionic Bond

The electrostatic forces of attraction between oppositely charged cations and anions.

Metals and non-metals usually form ionic bond in an ionic compound.

Sea of delocalised electrons in metal

Metallic Bond

The electrostatic forces of attraction between metal cations and a sea of delocalised electrons.

Only pure metals and alloys form metallic bonds.

Diamond has a giant molecular structure

Giant Molecular Structure

A huge 3D network of atoms held by strong covalent bonds in silicon dioxide, diamond and graphite.

1. High melting and boiling points
2. Insoluble in water and organic solvent
3. Do not conduct electricity (except graphite)
4. Diamond is hard but graphite is slippery

Regular arrangement of ions in a giant ionic lattice

Giant Ionic Lattice Structure

A huge 3D network of oppositely charged ions held by strong ionic bonds.

1. High melting and boiling points
2. Soluble in water but insoluble in organic solvent
3. Conducts electricity when aqueous or molten only

Metals have giant metallic structure

Giant Metallic Structure

A huge 3D network of metal cations in a sea of delocalised electrons held by strong metallic bond.

1. High melting and boiling points
2. Insoluble in water and organic solvent
3. Conducts electricity in all physical states
4. Malleable and ductile

Simple molecular structure contains very small molecules made up of just a few atoms

Simple Molecular Structure

A structure made up of discrete simple molecules held together by weak intermolecular forces of attraction.

1. Low melting and boiling points
2. Insoluble in water but soluble in organic solvent
3. Do not conduct electricity in all states

Intermolecular forces of attraction are weak and can be broken easily

Intermolecular Forces of Attraction

The attraction between different molecules, much weaker than the covalent bond within a molecule.

Intermolecular forces of attraction are also found between graphite layers.

Melting happens when bond is broken

Melting and Boiling Points

Higher melting and boiling points when bonds between particles are stronger, which require more energy to overcome.

1. Intermolecular forces of attraction are much weaker
2. For ionic bond, its strength is greater when the charge is larger

Electricity is the movement of ions or electrons

Electrical Conductivity

A substance can conduct electricity if it has mobile ions or delocalised electrons that are free-moving.

Giant metallic: delocalised electrons
Graphite: free-moving electrons
Giant ionic: mobile ions when aqueous or molten

Sugar is soluble in water

Solubility

A substance can dissolve when bonds between particles are overcome by interactions between solute and solvent.

Soluble in water: ionic compounds, sugar, alcohol
Soluble in organic solvent: simple molecules

Malleability and ductility are difficult words that mean flexibility

Malleability and Ductility

A malleable material can be hammered easily into different shapes, while a ductile one can be stretched into thin wires.

Metals are ductile and malleable as layers of metal ions can slide over each other easily through the sea of electrons, without disrupting the metallic bonding.

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