Lesson 6: Trends and Bonding

Question 1

Trends

Period 2 and 3

Answer 1

• The melting points of metals in period 2 and 3 increases along the period due to the giant structures these elements form.
• The melting points of the periods then decrease significantly because the non-metals form simple molecules, requiring less energy to break apart.

Question 2

Bonding

Metals vs Non-metals

Answer 2

• Metals exhibit metallic bonding.
• Non-metals exhibit simple covalent bonding within molecules or giant covalent bonding.

Question 3

Metals

Properties

Answer 3

• High melting points (except Ag).
• Good conductors.
• Insoluble in water.
• Ductile (wires).
• Malleable (moldable).

Question 4

Metals

Metallic Bonding

Answer 4

• Metals form very strong bonds.
• Electrons from the outer can become free.
• They form a sea of delocalised electrons which are free to move.
• This makes the atom positive.
• Electrons are negative.
• As they are opposite, they attract by strong electrostatic forces.

Question 5

Metals

Melting Point

Down a Group

Answer 5

• Melting points decrease because there are fewer delocalised electrons per atom while the cations (positive atoms) get stronger and heavier.
• This means the cations are held in place by a weaker force.
• Takes less energy to overcome this attraction.

Question 6

Metals

Melting Point

Across a Period

Answer 6

• Melting point increases because the amount of delocalised electrons per atom (and the cation charge) increases.
• Therefore, cations are held together by greater force of attraction.
• It takes more energy to break this attraction.

Question 7

Giant Covalent Structures

Description

Answer 7

• Some covalent structures are giant.
• Lots and lots of atoms joined together.
• The covalent bonds are very strong so they have a high melting point.
• These structures are not in molecules, so there are no intermolecular forces.

Question 8

Giant Covalent Structures

Example

Diamond

Answer 8

• 4 strong covalent bonds per carbon atom.
• Tetrahedral structure, 109.5° angles.
• Very high melting point.

Question 9

Giant Covalent Structures

Example

Graphite

Answer 9

• 3 strong covalent bonds + 1 delocalised electrons per C atom.
• Planes of carbon atoms in hexagons, 120° angles.
• High melting point.
• Malleable because the layers slide over each other (weak forces between layers).
• Delocalised electrons allows it to conduct electricity.