1.5 solid structures

Question 1

Describe the crystal structure of sodium chloride

Answer 1

Sodium chloride is a giant ionic crystal structure lattice made up on Na+ and Cl- ions held together with strong electrostatic attraction.

Na+ ions are smaller than Cl- ions.

Co-ordination numbers are 6:6

Question 2

Describe the crystal structure of caesium chloride

Answer 2

Caesium Chloride is a giant ionic crystal lattice made up of cs+ and cl- ions held together by strong electrostatic attraction. The structure is different to sodium chloride because the ions are of similar size so ions of the same type don’t come into contact with one another.
8:8 ratio

Question 3

Describe the structure of graphite

Answer 3

• each carbon bonded to 3 other carbons
• layers of hexagonal rings of carbon atoms form
• weak intermolecular forces between layers
• one delocalised electron per carbon atom

Question 4

Describe the structure of diamond

Answer 4

The carbon atom is covalently bonded to 4 other carbons forming a stronger tetrahedral formation to make a giant 3d structure.

Question 4

Properties of graphite

Answer 4

Soft and slippery because of the weak intermolecular forces between layers causing them to slide over one another.

Graphite conducts electricity because there is one delocalised electron per carbon atom. The delocalised electrons can carry charge.

Question 5

Properties of diamond

Answer 5

Very hard

High melting point

Doesn’t conduct electricity as there’s no charged particles.

Question 6

Iodine Structure

Answer 6

Covalent bonds between the iodine atoms and weak temporary dipole interactions between the molecules

Question 7

Explain why ice floats on water (ices structure)

Answer 7

Ice is a hydrogen-bonded lattice (1). In this structure, the water molecules are held further apart, making ice less dense (1). These hydrogen bonds are (partially) broken down in liquid water, allowing molecules to move closer together (1).

Question 8

electron sea model

Answer 8

all metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons

Question 8

Ionic solids

Answer 8

• solids that are composed of ions

Are hard, brittle and high melting points due to strong ionic bonds.

• Don’t conduct electricity as solids but when molten or dissolved in water they conduct due to ions being mobile when voltage is applied.

-some are soluble in water (most chlorides r soluble)

Question 9

Covalent solids properties

Answer 9

High melting points

Insoluble in water

Diamond is very hard because each carbon atom is bonded to 4 others which forms a 3d structure.

Graphite is softer as it has weaker layer structure so it’s used as a lubricant as layers slide over each other.

Graphite conducts electrify

Iodine is also soft and volatile

Question 10

uses of graphite

Answer 10

electrodes- graphite conducts electricy and has a high melting point

lubricant - graphite is slippery due to the layers which slide over each other

Question 11

metallic bonding

Answer 11

occurs in metals
positive metal ions are held together in a sea of delocalised ions