Structure

Question 1

What are the four main types of structure?

Answer 1

Ionic, Giant Covalent, Molecular Covalent, Metallic

Question 2

What state are molecular covalent substances usually in?

Answer 2

Gases, liquids or low melting point solids.

Question 3

What are examples of molecular covalent crystals?

Answer 3

Iodine I2, and Sulfur S8, Ice

Question 4

What are properties of molecular covalent crystals?

Answer 4

Low m.p / b.p due to weak intermolecular forces. Do not conduct electricity in any state because they have no free electrons.

Question 5

Give two examples of Giant Covalent crystals

Answer 5

Diamond and Graphite

Question 6

What are some properties of them (Diamond and graphite)

Answer 6

They have high m.p/b.p due to due to the covalent bonds between the atoms. Regular structure means that they are crystalline.

Question 7

Give the structure of diamond and graphite, and which conducts electricity?

Answer 7

Diamond - Each carbon is covalently boned to four others in a rigid tetrahedral arrangement
Graphite - Each carbon is covalently bonded to three others in a layered hexagonal structure, with Van der Waals forces between the layers.
The delocalised electrons in graphite can move and carry charge through the layers therefore it can conduct electricity when solid but not when molten because its structure is disrupted.

Question 8

What is the trend from sodium to argon?

Answer 8

Melting point increases from sodium to silicon then decreases to argon.

Question 9

Explain the trend from sodium to argon

Answer 9

1) Na to Al, the atoms can delocalise more electrons per atom thus have a higher m.p
2) Si has a Giant covalent structure thus has the highest m.p
3) P4, S8 and Cl2 are non-polar simple covalent molecules with low melting points as there are only Van der Waals between the molecules. Argon is monatomic

Question 10

What are the main features of ionic crystals?

Answer 10

High melting points, Soluble in water, conduct electricity when molten or aqueous

Question 11

What are the main features of molecular covalent crystals?

Answer 11

Low melting points, Insoluble in water and do not conduct electricity

Question 12

What are the main features of giant covalent crystals?

Answer 12

High melting points, insoluble in water and do not conduct electricity (except graphite)