CNC Illustration by Shuqi Tang

Chemical bonding

Chemical bonding is the answer to why atoms and ions are held together to form small molecules and giant structures.

SummaryResources

SUMMARY

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).

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 gain electrons to form negatively charged anions.

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.

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

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

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

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

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 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

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

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

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.

Resources

How to find the cation and anion in a compound?

What are ionic compounds and the ions they contain?

Dot and cross & other bonding diagrams

The art of chemistry: drawing dot-and-cross diagrams and more

Type of chemical bond quiz

Are you born to guess the type of bond?

Metallic bonding & giant metallic structure

Single ladies put your hands up! We’re paying homage to the metals that don’t need no one else to be stable, chemically of course.

Ions & ionic bonding

The story of give and take, in terms of electrons

The charge of ions quiz

Take charge of your learning by doing the quiz on ionic charge

Giant molecular structure: Diamond & graphite

Diamond and graphite, same same but different

Dot and cross diagrams of simple molecules

Dot the i's and cross the t's of your dot-and-cross diagrams

Simple molecular structure

Breathe in, and learn about the structure and physical properties of simple molecules found in your breath

Are ionic compounds soluble in water?

Chemistry is messy: most but not all ionic compounds are soluble in water

Giant ionic lattice structure

Be crystal clear about the physical properties of ionic compounds, as you look at minerals that make up the Earth