Bonding and Properties of Matter

Ionic compounds

• Giant structure of ions

• Held together by strong electrostatic forces of attraction between oppositely charged ions

• Forces act is every direction (3D)

Properties of ionic bonds / structures

• High melting and boiling point → strong electrostatic forces between oppositely charged ions → lot of energy required to break bonds

• Don’t conduct electricity when solid → ions in fixed positions

• Conduct when molten or dissolved in water → ions are free to move

Ionic compounds neutrality

Ionic compounds are electrically neutral.

→ positive and negative charges balance each other.

Simple covalent bonds characteristics

• Do not conduct electricity (no ions).

• Small molecules.

• Weak intermolecular forces: Low melting and boiling points.

Intermolecular forces when increased molecule size

They increase. (more electrons)

→ melting/boiling points to increase as well → more energy needed to overcome these forces

Polymers

Large molecules with atoms linked by covalent bonds.

• Strong intermolecular forces → solid at room temperature

Giant covalent structures characteristics

• Solids: atoms covalently bonded together in a giant lattice

• High melting/boiling points → strong covalent bonds.

• Mostly don't conduct electricity (no delocalised e−).

Examples of giant covalent substances

• Diamond, graphite, silicon dioxide.

Fullerenes

Hollow shaped molecules based on hexagonal rings.

C60

A spherical shape, simple molecular structure known as Buckminsterfullerene.

Nanotubes

Cylindrical fullerene with high length to diameter ratio.

High tensile strength

Strong bonds present in nanotubes.

What causes conductivity in nanotubes?

Delocalised electrons.

Graphene

A single layer of graphite.

Diamond (giant covalent structure) characteristics

• Has four strong covalent bonds for each carbon atom

• very hard

• very high melting point

• does not conduct electricity (no delocalised electrons)

Graphite (giant covalent structure) characteristics

• Has three covalent bonds for each carbon atom

• high melting point

• layers are free to slide → weak intermolecular forces → soft → used as lubricant

• conducts heat and electricity → one delocalised electron per each carbon atom

Alloys and being harder than pure metals

Mixtures of metals with other elements, usually metals.

• Different sized atom distort layers → harder for layers to slide over each other

Three states of matter

Solid, liquid and gas.

Nanoscience

Science that studies particles that are 1 - 100nm in size.

Nanoparticle

Small particles; 1-100 nm

Uses of nanoparticles

• Medicine (drug delivery systems)

• electronics

• lubricants

• catalysts

• Sun tan cream, deodorant