Moving from left to right across a period, the elements become less metallic. This is related to the increase in the number of electrons in the outer shell of their atoms. The atoms become more likely to gain or share electrons, rather than lose them when they form compounds.

Metals

Metals tend to have similar properties. They are always good conductors of electricity and heat, and they are always lustrous (shiny when cut). The majority of metals usually share these properties:

• high melting point
• hard (difficult to scratch)
• malleable (can be beaten into shape)
• ductile (can be pulled into wires)

There are some exceptions though. For example, mercury is a liquid at room temperature. The metals in Group 1, such as lithium, sodium and potassium, are all soft.

Non-metals

Non-metals have a variety of properties, but very few are good conductors of electricity. Graphite (a form of carbon) is a rare example of a non-metal that conducts electricity very well.

Many non-metals have low melting and boiling points. When non-metals are in a solid state, they are usually brittle so you can’t beat them into shape.

Metalloids

Some elements between the metals and non-metals in the periodic table have properties which are a mixture of the properties of metals and non-metals. These elements are called metalloids or semi-metals.These elements are found close to the zig-zag line that separates the metals from the non-metals.

Examples of metalloids

• Carbon – a dull, dark grey solid and is brittle (non-metallic properties) but has a high melting point and is a conductor of electricity and heat (metallic properties).
• Silicon – a shiny grey solid, an electrical conductor and has a high melting point (metallic properties) but is very brittle and has a low density (non-metallic properties).