Chemistry 2 Unit 1 and 2

A compound is 2 or more elements chemically combined together

A covalent bond is when atoms of non-metallic elements join together by sharing electrons

Ionic compound is a giant structure of ions formed when metallic and non-metallic elements react with each other

This is the electrostatic force of attraction between positive and negative ions

This is the bond in which when 2 two atoms Share one or more pairs of electrons

The atoms in metals are closely packed together and arranged in regular layers

The electrons in the highest energy level are delocalised. The strong electrostatic forces between these electrons and the positively charged metal ions hold the metal together

• They gave a giant structure
• Strong electrostatic forces that hold the ions together
• Lots of energy is needed to brake the bonds

Ionic compounds cannot conduct electricity when solid because the ions can only vibrate about fixed positions not move freely

Substances with simple molecules do not conduct electricity because the molecules do not have an overall electric charge

Substances with simple molecules have a low melting/boiling point because they have weak intermolecular forces between molecules

They have a high melting/boiling point because of the large amounts if energy needed to brake the many strong bonds

Giant covalent structures or macromolecules

Diamond is a form of carbon that had a regular 3D giant structure. Every carbon atone is covalently bonded to 4 other carbon atoms.

In graphite, each carbon atom bonds to 3 other carbon atoms forming layers. There are no covalent bonding between the layers therefore they slide over each other

Graphite can conduct electricity because one electron from each carbon atom is delocalised

Graphite has week intermolecular forces between the layers

Fullerenes are large molecules formed from hexagon rings of carbon atoms, with different numbers if carbon atoms

• Fullerenes can be used for:
• Drug delivery into the body
• Lubricants
• Catalysts
• Reenforcing materials

Metals can be bent and shaped because the layers if atoms in metals are able to slide over each other

Alloys are mixtures of metals or metals and elements

Alloys are harder than pure metals because the different sized atoms in the mixture distort the layers in the metal structure and make it more difficult for them to slide over each other

Shape memory alloys can return to their original shape when heated after being deformed. ( e.g. Dental braces)

Metal structures have delocalised electrons that move throughout the giant metallic lattice and can transfer energy quickly

They are made using different reaction conditions and catalysts. HD poly(ethene) had a higher softening temperature and is stronger than LD

Thermo-softening polymers are made up of individual polymer chains tangled together. they have week intermolecular forces

Nanoscience is the study if small particles that are between 1-100 NM

They contain a few hundred atoms arranged in a particular way; their small size give them a large surface area to volume ratio

• Nano particles can be used for:
• High selective sensors
• Very efficient catalysts
• New coatings
• Cosmetics e.g. Sun screen and deodorants