Mixtures, compounds and elements

Metals, metalloids and non-metals

The elements in the Periodic Table can also be divided according to whether they are metals , metalloids or non-metals . On the right hand side of the Periodic Table you can draw a 'zigzag' line (This line starts with Boron ( $\mathrm{B}$ ) and goes down to Polonium ( $\mathrm{Po}$ ). This line separates all the elements that are metals from those that are non-metals. Metals are found on the left of the line, and non-metals are those on the right. Along the line you find the metalloids. You should notice that there are more metals then non-metals. Metals, metalloids and non-metals all have their own specific properties.

Metals

Examples of metals include copper ( $\mathrm{Cu}$ ), zinc ( $\mathrm{Zn}$ ), gold ( $\mathrm{Au}$ ), silver ( $\mathrm{Ag}$ ), tin ( $\mathrm{Sn}$ ) and lead( $\mathrm{Pb}$ ). On the Periodic Table, the metals are on the left of the zig-zag line. There are a large number of elements that are metals. The following are some of the properties of metals:

• Thermal conductors Metals are good conductors of heat. This makes them useful in cooking utensils such as pots and pans.
• Electrical conductors Metals are good conductors of electricity. Metals can be used in electrical conducting wires.
• Shiny metallic lustre Metals have a characteristic shiny appearance and so are often used to make jewellery.
• Malleable This means that they can be bent into shape without breaking.
• Ductile Metals (such as copper) can be stretched into thin wires, which can then be used to conduct electricity, as well as for other uses.
• Melting point Metals usually have a high melting point and can therefore be used to make cooking pots and other equipment that needs to become very hot, without being damaged.

You can see how the properties of metals make them very useful in certain applications.

Group work : looking at metals

1. Collect a number of metal items from your home or school. Some examples are listed below:
   • hammer
   • wire
   • cooking pots
   • jewellery
   • nails
   • coins
2. In groups of 3-4, combine your collection of metal objects.
3. What is the function of each of these objects?
4. Discuss why you think metal was used to make each object. You should consider the properties of metals when you answer this question.

Non-metals

In contrast to metals, non-metals are poor thermal conductors, good electrical insulators (meaning that they do not conduct electrical charge) and are neither malleable nor ductile. The non-metals are found on the right hand side of the Periodic Table, and include elements such as sulphur ( $\mathrm{S}$ ), phosphorus ( $\mathrm{P}$ ), nitrogen ( $\mathrm{N}$ ) and oxygen ( $\mathrm{O}$ ).

Metalloids

Metalloids or semi-metals have mostly non-metallic properties. One of their distinguishing characteristics is that their conductivity increases as their temperature increases. This is the opposite of what happens in metals. This property is known as semi-conductance and the materials are called semi-conductors. Semi-conductors are important in digital electronics, such as computers. The metalloids include elements such as silicon ( $\mathrm{Si}$ ) and germanium ( $\mathrm{Ge}$ ). Notice where these elements are positioned in the Periodic Table.

You should now be able to take any material and determine whether it is a metal, non-metal or metalloid simply by using its properties.