SC7 - Types of Substance ✓

Atoms of more than one element joined together by chemical (covalent) bonds

• They are formed of covalent bonds • While there are strong covalent bonds, the forces between molecules are weak meaning they require little energy to break

• For something to be able to conduct electricity it must contain a charged particle that is free to to move. • Covalent bonds aren’t based on charges tso it doesn’t meet these requirements

• Monomers are small simple molecules. • When multiple of these join up in a chain, they form a polymer

Different structural forms of the same element

• Fullerenes are spherical or tubular structures where each carbon atom is bonded to three others • They have low m.p/b.p due to weak intermolecular forces • They are also soft and slippery • Can conduct electricity due to delocalised electron

• Flat shape that cna be rolled up • Each carbon atom is bonded to threee others meaning there is a delocalised electron allowing conduction of electricity • Low m.p/b.p

• High melting point due to strong covalent bonds • Layers easily slide over eachother due to weak forces between them • Three bonds per carbon atom • Delocalised electron allows conduction of electricity • Useful as a lubricant due to layers sliding • Used for electrolysis as it is unreactive and cheap

• Tetrahedral structure • Four bonds per carbon atom • Electrical insulatro due to no free electrons • High melting point due to strong covalent bonds • Very strong due to tetrahedral structure • Used for drills due to strength

Giant molecular structures: Huge 3D netwroks of atoms linked by bonds

• Metals are bonded in a giant lattice structure • They are held together by the stron electrostatic forces of attraction that exist between the positive metal ions and the negative delocalised electons • Strong electrostatic forces of attraction require a lot of energy to break giving them high m.p/b.p • Delocalised electron allows it to conduct electricity • They are also malleabele

• Mallebale means that it can change shape and bend without breaking • Metals are a giant lattice structure of positive metal ions delocalised electrons • When a force is applied to a metal, the layers slide over each other • It doesn’t break because of the ‘sea’ of delocalised electrons holding the metal together by electrostatic forces

• To be able to conduct electricity, something must contain a charged particle that is free to move • Since metals have a sea of deloclised electrons, it meets these two requirements • When a potenital difference is applied, the electrons move to the positive side

• As the charge of the ion increases, the number of delocalised electrons per atom increases. • This increases the electrical conductivity

Pros: • Shows how electrons are shared in covalent and ionic bonds Cons: • Do not show the structure formed • Suggests that electrons are different

Pros: • Shows it is held in a lattice • Explains properties such as eletical conductivity Cons: • Doesn’t show the ions to be constantly vibrating

Pros: • They show the structure that is formed • They show the number of bonds per atom Cons: • The atoms are too far apart • There aren’t actually any ‘sticks’