first half of chemistry flash cards

How are covalent bonds formed

By atoms sharing electrons

Which type of atoms form covalent bonds between them?

Non metals

Describe the structure and bonding of a giant covalent substance

Billions of atoms bonded together by strong covalent bonds

Describe the structure and bonding of small molecules

Small numbers of atoms group together into molecules with strong covalent bonds between the atoms and weak intermolecular forces between the molecules

Describe the structure and bonding of polymers

Many identical molecules joined together by strong covalent bonds and long chain, with weak intermolecular forces between the chains

Why do giant covalent structures have high melting points?

It takes a lot of energy to break the strong covalent bonds between the atoms

Why do small molecules have low melting points?

Earliest small amount of energy is needed to break the week into molecular forces

Why do large molecules have higher melting and boiling points than small molecules?

The intermolecular forces are stronger in large molecules

Why do most covalent substances not conduct electricity?

Do not have delocalised electrons or ions

Describe the structure and bonding in graphite

Each carbon items are bonded with three others in hexagonal rings arranged in layers - it has delocalised electrons and weak forces between the layera

Why can graphite conduct electricity?

The delocalised electrons can move through the graphite

Explain why graphite is soft

Layers are not bonded so can slide over each other

What is graphene?

One layer of graphite

Give two properties of graphene?

Strong, conducts electricity

What is a fullerene

Hollow cage of Carbon atoms arranged as a sphere or a tube

What is a nanotube

Hollow cylinder of carbon atoms

Give 2 properties of nanotubes

High tensile strength, conducts electricity

Give three uses of fullerenes

Lubricants, drug delivery (spheres), high tech electronics

What is an ion

Atom that has lost or gained electrons

Which kind of elements form ionic bonds?

Metals and non metals