2.2.2 Bonding and structure

Question 1

What are the 3 main types of chemical bonds?

Answer 1

Ionic, metallic and covalent

Question 2

Define ionic bonding.

Answer 2

The electrostatic attraction between positive and negative ions

Question 3

Define covalent bonding.

Answer 3

The strong electrostatic attraction between a shared pair of electrons and the nucelus of the bonded atoms.

Question 4

Define metallic bonding.

Answer 4

Electrostatic attraction between the positive metal ions and the sea of delocalised electrons.

Question 5

Why do giant ionic lattices conduct electricity when liquid but not when solid?

Answer 5

• In a solid state the ions are fixed in the lattice due to the electrostatic forces of attraction so they cant carry a charge
• In a liquid or molten state the forces have been broken, so the ions are free to move and can carry a current.

Question 6

Why do giant ionic lattices have high melting and boiling points?

Answer 6

As it takes a large amount of energy to overcome the electrostatic forces of attraction
- The higher the charge the higher the m.p/b.p

Question 7

Why are giant ionic lattices soluble in polar solvents?

Answer 7

Polar solvents attract ions out of the lattice into the solution.

Question 8

What are single covalent bonds?

Answer 8

• known as ‘sigma’ bonds
• represents 2 electrons in a pair

Question 9

What are double covalent bonds?

Answer 9

• 4 shared electrons
• only C, N, O can form these

Question 10

What are triple covalent bonds?

Answer 10

• 6 shared electrons
• only C, N can form these

Question 11

What is a lone pair?

Answer 11

Electrons in the outer shell of an atom which are not involved in bonding.

Question 12

What is a dative covalent bond?

Answer 12

• a bond where both of the shared electrons are supplied by one atom
• for this to happen the acceptor ion must be electron deficient
• a dative bond is treated the same as a covalent bond
• can be shown in a diagram by an arrow pointing away from the lone pair

Question 13

What does expansion of the octet mean?

Answer 13

When a bonded atom has more than 8 electrons in the outer shell

Question 14

What are the 2 types of covalent structure?

Answer 14

• simple molecular lattice
• giant covalent lattice

Question 15

Describe the bonding in simple molecular structures.

Answer 15

Atoms within the same molecule are held by strong covalent bonds. Different molecules are held by weak intermolecular forces.

Question 16

What are two examples of simple molecular structures?

Answer 16

iodine: the two I atoms are held together by a covalent bond, but the molecules are held together by london forces
Ice: The H and O atoms are held together by covalent bonds but the molecules are held together by hydrogen bonds

Question 17

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

Answer 17

As only a small amount of energy is needed to overcome the weak intermolecular forces

Question 18

Why do simple molecular structures not conduct electricity?

Answer 18

As there are no free ions or electrons; all electrons are fixed in covalent bonds

Question 19

What type of solvent do simple molecular structures dissolve in?

Answer 19

Non polar solvents

Question 20

Give examples of giant covalent structures

Answer 20

Diamond, graphite and silicon dioxide

Question 21

What are 3 properties of giant covalent structures?

Answer 21

• high melting and boiling point
• non conductors of electricity except graphite
• insoluble in polar and non polar solvents

Question 22

How does graphite conduct electricity?

Answer 22

Delocalised electrons present between the layers are able to move freely carrying the charge.

Question 23

Why do giant covalent structures have high melting and boiling points?

Answer 23

Strong covalent bonds within the molecules need to be broken which requires al ot of energy

Question 24

Describe the structure of diamond.

Answer 24

3D tetrahedral structure of C atoms, with each C atom bonded to 4 others