7.3 - Periodic Trends - Bonding and Structure

Question 1

What are metalloids?

Answer 1

An element whose properties are intermediate of metals and non-metals.

Question 2

What are constant properties of almost all metals?

Answer 2

• All conduct electricity

- All metals bar mercury are solid at room temperature

Question 3

Describe the process of metallic bonding.

Answer 3

Each atom in a solid metal structure donates 1 electron to a pool of delocalised electrons - which are mobile throughout the structure.
- This leaves cations in fixed positions which maintain the structure.

Metallic Bonding: The electrostatic attraction between cations and delocalised electrons

• Metallic structures have no charge as there are as many ionic charges as there are delocalised electrons.

Question 4

Define giant metallic lattice.

Answer 4

3D structure of +ve ions and deloclised electrons bonded by strong metallic bonds with many atoms

Question 5

What are the properties of metals?

Answer 5

High electrical conductivity - Solid state metals can conduct electricity due to the delocalised electrons being mobile and being able to carry a charge.

High MP/BP - MP/BP depends on strength of metallic bonds. Strong electrostatic attraction means more energy required to break the bonds.

Metals are Insoluble
Metals have Strong Electrostatic Forces of Attraction

Question 6

Define giant covalent structure and elements that have it.

Answer 6

3D structure of billions of atoms bonded by strong covalent bonds (has no intermolecular force)
- Carbon and silicon in Group 4

Question 7

Describe the giant covalent structures of carbon and silicon.

Answer 7

Both carbon (except in graphite and graphene) use their 4 electrons to bond to make giant covalent structures with no delocalised electrons. 
- Diamond - tetrahedral bond angle 109.5

Question 8

What are the properties of giant covalent structures?

Answer 8

High MP/BP - large amounts of energy needed to overcome string covalent bonds (no intermolecular forces)

Giant Covalent Lattices are Insoluble - covalent bonds too strong to be broken by solvent interaction

Giant Covalent Lattices are non-electrical conductors - no delocalised electrons - except for graphite and graphene

Question 9

What are periodic trend in melting points?

Answer 9

Across Period 2 & 3…
- Increase in MP from G1>G4
- Sharp decrease from G4>G5 - signals change from giant structures of G1>G4 to simple molecular structures with int molecular forces
G5>8 low MP