Structure and Bonding (giant covalent structures, metallic bonding, trends in intermolecular forces)

Question 1

What are the 2 different types of covalent structures that you can have?

Answer 1

1. Simple molecular substances
2. Giant covalent lattices

Question 2

What is a simple molecular substance?

Answer 2

it is made up of simple molecules, e.g. H2, H20

Question 3

What structure do simple molecules form in the solid state?

Answer 3

A regular structure called a simple molecular lattice

Question 4

What are the molecules held together by in a simple molecular lattice?

Answer 4

• weak intermolecular forces, while the atoms are bonded together by strong covalent bonds

Question 5

What are the three properties of simple molecular substances?

Answer 5

1. Low melting and boiling points
2. Insoluble in water
3. Do not conduct electricity

Question 6

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

Answer 6

because not much energy is needed to break the weak intermolecular forces

Question 7

Explain the property of solubility

Answer 7

• Non-polar molecules are insoluble in polar substances, but soluble in non-polar
• Polar molecules are insoluble in non-polar substances, but soluble in polar substances

Question 8

Why do simple molecular substances not conduct electricity?

Answer 8

• As there are no free charged particles (ions or electrons) in simple molecular structures
• so there is nothing to carry a charge

Question 9

What is a giant covalent lattice?

Answer 9

A structure where many billions of atoms are held together by a network of strong covalent bonds

Question 10

What are the 4 giant covalent lattices you need to be aware of?

Answer 10

1. Diamond
2. Graphite
3. Graphene
4. Silicon Dioxide (sillica)

Question 11

State two properties of giant covalent lattices?

Answer 11

1. High melting points
2. Insoluble in most solvents

Question 12

Why do giant covalent lattices have high melting points?

Answer 12

As high temperatures are necessary to provide the energy required to break the many strong covalent bonds in the lattice structure

Question 13

Why are giant covalent lattices insoluble in almost all solvents?

Answer 13

As the bonds are far too strong to be broken by interaction with solvents

Question 14

What is metallic bonding?

Answer 14

The strong electrostatic attraction between the cations and the delocalised electrons

Question 15

What is a giant metallic lattice?

Answer 15

billions of metal atoms held together

Question 16

Why do giant metallic lattices have high melting points and why are they usually solid at room temperature?

Answer 16

As high temperatures are needed to overcome the strong electrostatic attraction between the cations and delocalised electrons

Question 17

Why do metals conduct electricity as both solids and liquids?

Answer 17

as the delocalised electrons are able to move throughout the structure

Question 18

Why do metals not dissolve in water?

Answer 18

as any interaction would lead to a reaction, rather than the metal dissolving

Question 19

What are the two anomalous properties of water due to hydrogen bonding?

Answer 19

1. Relatively high melting and boiling points
2. Ice having a much lower density than liquid water

Question 20

Why does water have relatively high melting and boiling points?

Answer 20

Due to the strong hydrogen bonds that require a lot of energy to overcome

Question 21

Why does ice have a lower density than water?

Answer 21

• ice has an open lattice structure
• where the hydrogen bonds in ice hold the molecules in a rigid structure with lots of air gaps