1.10 Aggregates

What are aggregates and why are they important

aggregates are groups of particles that are held together by attractive forces

these can be groups of molecules but groups of the atoms may also qualify

They are important as properties of pure substances (either element or compound) rely on aggregates and not individuals particles

what are the 4 types of aggregates

• Ionic crystals

• molecular crystal

• metallic crystal

• network solids

Gasses are not included, as gasses do not form aggregates due to low IMFs

Ionic crystals, what are they?

Ionic compounds are formed from ionic bonds; these ionic bonds of oppositely charged ions layer into compact structures known as ionic crystals

• they have strong electrostatic forces causing high melting points

• they are often hard and brittle

• and they only conduct electricity in liquid form

What is a molecular crystal

These are crystals formed from the layering of covalent molecules. (polar, non-polar, coordinate)

• usually soft with low melting points

• very little electrical conductivity

what is a metallic crystal

Metallic crystals are formed from the layering of metal atoms in an entirely metal substance.

• metal atoms are stacked, leaving electrons with space in between to move, allowing for high conductivity

• very high melting point

• malleable

What is Network solid

Network solids are composed of non-metal atoms on a single element

there are so many non-metals, each with their own unique network solid properties

What is are allotropes

allotropes are network solids of the same non-metal that possess different arrangements

what are the three carbon allotropes

• Graphite

• Diamond

• Fullerenes

Graphite properties and arrangement

• high melting point

• formed from hexagonal arangement of carbon with only three bound electrons per carbon leaving a single electron unpaired allowing for electrical conductivity

• bonded in places leaving it slippery

• soft and flexible due to london force bonds between planes

Diamond

• Incredibly high melting point and durability due to compactly packed tetrahedrally arranged carbons

• does not conduct electricity

Fullerenes

A fullerene is takes the shape of either a sphere (called a buckyball) or a cylinder (called a nanotube) throug hexagonally bonded carbons, each with 4 binds.