Structure and bonding

Ionic bond definition

When a metal donates electrons to a non-metal- forms oppositely charged attracted ions

Covalent bond definition

A pair of shared electrons between two non-metals

Metallic bond definition

Positive metal ions in a ‘sea’ of delocalised electrons

Polymer definition

Long chain molecule made of repeating monomers

Monomer definition

Small molecules that join to make polymers- polymers linked to other atoms by strong covalent bonds- strong intermolecular forces

Delocalised definiton

Electrons free to move anywhere- carry electricity and thermal energy

Alloy definition

A mixture of a metal and another element- changes qualities

Properties of ionic compounds e.g. sodium chloride

• high density

• high mp and bp- energy needed to break strong bonds

• conduct electricity dissolved or melted- ions free to move and carry current

• don’t conduct heat

• brittle

• held together by electrostatic forces of attraction

Properties of small covalent molecules e.g. oxygen

• low density

• low mp and bp

• don’t conduct electricity or heat- no electric charge

• weak intermolecular forces THESE ARE BROKEN DURING CHANGE OF STATE NOT THE BONDS

  • increase with size of molecule- larger molecules have higher mp and bp

Properties of giant covalent structures e.g. diamond

• high density

• high mp and bp

• only graphite conduct electricity

• only diamond conduct heat

• brittle

• linked to other structures by strong covalent bonds

  • these bonds must be overcome to change substance

Properties of metals and alloys e.g. steel

• high density

• high mp and bp

• conduct electricity and heat

• malleable

• layers can slide over each other- can be bent and shaped in metals

• in alloys, different sized atoms, distort layers, harder to slide, stronger than metals

Features of diamond

• 4 bonds between each carbon atom covalent

• no delocalised electrons

• very hard

• no conduct elec

• high mp

• used in gems

Features of graphite

• 3 bonds between each carbon atom covalent- forms layers of hexagonal rings with no bonds between layers (only weak intermolecular forces)

  • layers can slide over each other- soft

• one delocalised electron from each carbon atom

• soft

• conduct elec

• high mp

• used in pencils

Features of graphene/ fullerene

• single layer of graphite

• Flexible + strong- atoms within layers very tightly bonded

• elastic- planes of atom can flex without atoms breaking

• fullerenes- carbon atoms with hollow shapes

• nanotubes- cylindric fullerenes- useful for nanotechnology and electronics

  • used as lubricants, to deliver drugs in body and catalysts

  • reinforcing materials e.g. tennis rackets

Particle theory

• amount of energy needed to change state depends on the strength of the forces

• stronger forces=higher melting and boiling points

• no forces shown in simple ball model