5.3 Metallic bonding

Metallic bonds

The nature of the metallic bond

The structure of a metallic bond is quite different from covalent and ionic bonds. In a metal bond, the valence electrons are delocalised , meaning that an atom's electrons do not stay around that one nucleus. In a metallic bond, the positive atomic nuclei (sometimes called the 'atomic kernels') are surrounded by a sea of delocalised electrons which are attracted to the nuclei ( [link] ).

Metallic bond

Metallic bonding is the electrostatic attraction between the positively charged atomic nuclei of metal atoms and the delocalised electrons in the metal.

Activity: building models

Using coloured balls and sticks (or any other suitable materials) build models of each type of bonding. Think about how to represent each kind of bonding. For example, covalent bonding could be represented by simply connecting the balls with sticks to represent the molecules, while for ionic bonding you may wish to construct part of the crystal lattice. Do some research on types of crystal lattices (although the section on ionic bonding only showed the crystal lattice for sodium chloride, many other types of lattices exist) and try to build some of these. Share your findings with your class and compare notes to see what types of crystal lattices they found. How would you show metallic bonding?

You should spend some time doing this activity as it will really help you to understand how atoms combine to form molecules and what the differences are between the types of bonding.

Chemical bonding

1. Give two examples of everyday objects that contain..
   1. covalent bonds
   2. ionic bonds
   3. metallic bonds
2. Complete the table which compares the different types of bonding:

   	Covalent	Ionic	Metallic
   Types of atoms involved
   Nature of bond between atoms
   Melting Point (high/low)
   Conducts electricity? (yes/no)
   Other properties

3. Complete the table below by identifying the type of bond (covalent, ionic or metallic) in each of the compounds:

   Molecular formula	Type of bond
   $\mathrm{H}{}_2\mathrm{SO}{}_4$
   $\mathrm{FeS}$
   $\mathrm{NaI}$
   $\mathrm{MgCl}{}_2$
   $\mathrm{Zn}$

4. Which of these substances will conduct electricity most effectively? Give a reason for your answer.
   
5. Use your knowledge of the different types of bonding to explain the following statements:
   1. Swimming during an electric storm (i.e. where there is lightning) can be very dangerous.
   2. Most jewellery items are made from metals.
   3. Plastics are good insulators.