MYP 9 Unit 3

Structure and bonding: 9.3.8: Metals and metallic bonding

Objectives

  • To know that metal bonding involves a lattice of ions surrounded by a sea of delocalised electrons
  • To know the general properties of metals and how they relate to the metallic structure
  • To understand that alloys have more desirable properties than the constituent elements

Introduction

Helen and Cassandra video

Stone age

Bronze age

Iron age

Class activity

Research metals and metallic structures

Teacher's notes

The lesson is mainly discussion

Resources

Helen and Cassandra

Metallic bonding

 

E-assessment

C2.2.3 Covalent structures

a) Atoms that share electrons can also form giant structures or macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms. All the atoms in these structures are linked to other atoms by strong covalent bonds and so they have very high melting points.

Candidates should be able to recognise other giant structures or macromolecules from diagrams showing their bonding

b) In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.

c) In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.

Higher Tier candidates should be able to explain the properties of graphite in terms of weak intermolecular forces between the layers.

d) In graphite, one electron from each carbon atom is delocalised. These delocalised electrons allow graphite to conduct heat and electricity.

Candidates should realise that graphite is similar to metals in that it has delocalised electrons.

e) Carbon can also form fullerenes with different numbers of carbon atoms. Fullerenes can be used for drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials, eg in tennis rackets.

Candidates' knowledge is limited to the fact that the structure of fullerenes is based on hexagonal rings of carbon atoms


Next Page


IsisSoft 2014