GCSE Chemistry AQA C2

What are the three main types of strong chemical bonding?

Ionic, covalent and metallic bonding

In which type of substances does ionic bonding occur?

In compounds formed from metals combined with non-metals

In which type of substances does covalent bonding occur?

In non-metallic elements and in compounds of non-metals

In which type of substances does metallic bonding occur?

In metallic elements and alloys

What happens to electrons during ionic bonding?

Metal atoms lose electrons to form positive ions and non-metal atoms gain electrons to form negative ions

What is an ionic bond?

A strong electrostatic attraction between oppositely charged ions

What is a covalent bond?

A shared pair of electrons between two non-metal atoms

What is a metallic bond?

The electrostatic attraction between positive metal ions and delocalised electrons

What charge do ions from Group 1 elements form?

+1

What charge do ions from Group 2 elements form?

+2

What charge do ions from Group 6 elements form?

-2

What charge do ions from Group 7 elements form?

-1

What is a giant ionic lattice?

A three-dimensional regular arrangement of alternating positive and negative ions

What state of matter has a fixed shape and volume with particles vibrating in fixed positions?

Solid

What state of matter has a fixed volume but takes the shape of its container with particles closely packed but moving past each other?

Liquid

What state of matter has no fixed shape or volume with particles far apart and moving rapidly in all directions?

Gas

What are the four state symbols used in chemical equations?

(s) solid, (l) liquid, (g) gas and (aq) aqueous

What does the aqueous (aq) state symbol mean?

The substance is dissolved in water

What are three limitations of the simple particle model?

Particles are drawn as solid spheres, forces between particles are not shown, and particle sizes are not to scale

Why do ionic compounds have high melting and boiling points?

They have a giant lattice structure with strong electrostatic forces between oppositely charged ions requiring lots of energy to break

Why can ionic compounds conduct electricity when molten or dissolved in water?

The ionic lattice breaks down so ions become free to move and carry electrical charge

Why can ionic compounds not conduct electricity when solid?

The ions are held in fixed positions in the lattice and cannot move

What are simple molecular substances?

Substances made of small molecules containing strong covalent bonds between atoms

Why do simple molecular substances have low melting and boiling points?

They have weak intermolecular forces between molecules which require little energy to overcome

What happens to intermolecular forces as the size of a simple molecule increases?

Intermolecular forces increase, leading to higher melting and boiling points

Why do simple molecular substances not conduct electricity?

They do not have free-moving electrons or ions to carry an electrical charge

What is a polymer?

A very large molecule made of many repeating units (monomers) joined by covalent bonds

Why are most polymers solid at room temperature?

They are large molecules so the intermolecular forces between polymer chains are relatively strong

What is a giant covalent structure?

A structure containing millions of atoms linked together by strong covalent bonds in a continuous lattice

Name three examples of giant covalent structures

Diamond, graphite and silicon dioxide (silica)

Why do giant covalent structures have extremely high melting points?

A massive amount of energy is needed to break the many strong covalent bonds throughout the structure

Describe the structure and bonding of diamond

Each carbon atom forms four strong covalent bonds with other carbon atoms in a rigid giant tetrahedral structure

Why is diamond extremely hard?

It has a rigid giant covalent structure where every carbon atom is held by four strong covalent bonds

Why does diamond not conduct electricity?

It has no free electrons or ions to carry electrical charge

Describe the structure and bonding of graphite

Each carbon atom forms three covalent bonds, creating hexagonal layers held by weak intermolecular forces with delocalised electrons

Why is graphite soft and slippery?

The hexagonal layers are held together by weak intermolecular forces so they can slide over each other easily

Why can graphite conduct electricity and thermal energy?

Each carbon atom has one delocalised electron that is free to move throughout the structure and carry charge/heat

What is graphene?

A single layer of graphite that is one atom thick

State three properties of graphene

Extremely strong, very light, and an excellent conductor of electricity and thermal energy

What is a fullerene?

A molecule of carbon atoms with hollow shapes based on hexagonal, pentagonal or heptagonal rings

What was the first fullerene to be discovered?

Buckminsterfullerene (C60)

What shape is Buckminsterfullerene?

A hollow sphere made of 60 carbon atoms

What are carbon nanotubes?

Cylindrical fullerenes with very high length-to-diameter ratios

State three useful properties of carbon nanotubes

High tensile strength, high electrical conductivity, and high thermal conductivity

Give three uses of fullerenes

Drug delivery into the body, as industrial catalysts, and as lubricants

Describe the structure and bonding of a metal

A giant structure of positive metal ions arranged in regular layers surrounded by a sea of delocalised electrons

Why do metals conduct electricity and thermal energy well?

The delocalised electrons are free to move throughout the entire structure and carry electrical charge and thermal energy

Why are pure metals malleable and ductile?

The metal ions are arranged in uniform layers that can easily slide over each other when a force is applied

What is an alloy?

A mixture of two or more elements, at least one of which is a metal

Why are alloys harder than pure metals?

Different sized atoms disrupt the regular layers, making it harder for the layers to slide over each other

What is nanoscience?

The study of structures that are 1 to 100 nanometres in size

What is the size range of nanoparticles?

1 nm to 100 nm (a few hundred atoms)

What is the size range of fine particles (PM2.5)?

100 nm to 2500 nm (0.1 to 2.5 micrometres)

What is the size range of coarse particles or dust (PM10)?

2500 nm to 10,000 nm (2.5 to 10 micrometres)

What happens to the surface area to volume ratio of a particle as its side length decreases by a factor of 10?

Its surface area to volume ratio increases by a factor of 10

Why do nanoparticles have different properties from bulk materials?

They have a very high surface area to volume ratio, making them much more reactive

Give four potential uses of nanoparticles

In sunscreens, medicines, catalysts, electronics, and deodorants

Give a potential advantage of using nanoparticles in sunscreens

They provide better protection against UV rays and do not leave white marks on skin

Give a potential risk or concern regarding the use of nanoparticles

They could be absorbed through the skin into the bloodstream or inhaled into lungs with unknown long-term health effects