Covalent structures

Question 1

What are the two types of covalent structures?

Answer 1

simple covalent molecular structure

giant covalent molecular structure

Question 2

Name three types of simple molecular structures.

Answer 2

iodine, water, methane, oxygen, methanol

Question 3

What are the three main properties of simple molecular structures and why this is the case?

Answer 3

• have a low melting and boiling point- weak intermolecular forces
• can’t conduct electricity- no free electrons that can move and carry a charge
• they are usually a liquid/ gas at room temperature (except iodine)- have low boiling points

Question 4

Ammonia is gas at room temp. Explain why ammonia has a low boiling point.

Answer 4

• Ammonia is a simple covalent molecular structure

- weak intermolecular forces so less energy is required to overcome it

Question 5

What does intermolecular and intramolecular mean?

Answer 5

intermolecular: between molecules
intramolecular: within molecules

Question 6

What is an allotrope?

Answer 6

same element but different structures

Question 7

What are the natural allotropes of carbon?

Answer 7

diamond and graphite

Question 8

What is it meant by giant covalent molecular structures?

Answer 8

a regular repeated 3d arrangement of carbon atoms

Question 9

Name the properties of diamonds.

Answer 9

STRUCTURE: each carbon atom is bonded to four other carbon atoms, no free moving electrons
MELTING POINT: high
HARD OR SOFT: hard
ELECTRICAL/THERMAL CONDUCTIVITY: doesn’t conduct either
USES: jewellery, cutting tools

Question 10

Name the properties of graphite.

Answer 10

STRUCTURE: each carbon atom is bonded to three other carbon atoms, layered structure with delocalised electrons
MELTING POINT: high
HARD OR SOFT: soft
ELECTRICAL/THERMAL CONDUCTIVITY: does conduct both
USES: pencils, lubricants, electrodes

Question 11

Name the man-made allotropes of carbon

Answer 11

Graphene, buckyballs, nanotubes

Question 12

Name the properties of graphene

Answer 12

• almost transparent
• strong, 2d structures
• conducts electricity
• used for flexible phones

Question 13

Name the properties of buckyballs

Answer 13

• spherical fullerene made up of 60 carbon atoms

- used for drug delivery into cells, lubricant

Question 14

Name the properties of nanotubes

Answer 14

• strong

- used to reinforce some sports equipment (tennis rackets)