Metals and Non-metals

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The easiest way to start grouping substances is by comparing their physical properties.

Physical properties include appearance, texture, colour, odour, melting point, boiling point, density, solubility, polarity, and many others.

1. Physical state - Metals are solids at room temperature e.g. sodium, aluminium, potassium, magnesium. There are exceptions to this. Mercury and gallium are metals but they are in liquid state at room temperature.
2. Lustre – Metals have a shining surface called lustre when freshly prepared. They have a quality of reflecting light from their surface and they can be polished e.g. metals like gold, silver, copper show this property.
3. Malleability - Metals can be beaten into thin sheets. This property is called malleability. Due to this property, metals can be rolled into sheets e.g. aluminium, copper, zinc can be beaten into sheets.
4. Ductility - Metals can be drawn into thin wires. This property is called ductility. For example, 100 grams of silver can be drawn into a thin wire about 200 meters long.
5. Hardness – Metals are generally hard e.g. iron, cobalt, nickel. There are few exceptions to this. Sodium and potassium are soft and they can be cut with a knife.
6. Sound - Metals produce ringing sound, so, metals are called sonorous. The sound of metals is also known as metallic sound. This is the cause that metal wires are used in making musical instruments.
7. Conduction – Generally, metals are good conductors of heat and electricity because they have free electrons. Silver and copper are the two best conductors. Relatively, lead and bismuth are poor conductors of heat and electricity.
8. Density - Metals generally have high density and they are heavy. Iridium and osmium have the highest densities while lithium has the lowest density.
9. Melting and boiling point – Metals usually have a high melting point and boiling point. For example, iron, cobalt and nickel have high melting and boiling point. Tungsten has the highest melting point. There are some exceptions to this. For example, most of the alkali metals have low melting and boiling point.
10. Strength - Most of the metals are strong and have high tensile strength. Because of this big
    structures are made using metals, such as copper and iron.
11. Sonorous - Metals produce a sound on striking a hard surface.

Physical state – Non-metals can exist in solid or liquid or gaseous state at room temperature.  For example, carbon, sulphur, phosphorus, iodine are in the solid state, bromine is in a liquid state while oxygen, nitrogen, chlorine are in the gaseous state at room temperature.

Lustre – Non-metals do not have lustre. They do not reflect light from their surface. (exception – diamond and iodine ) Non-metals have a dull appearance. For example, sulphur, phosphorus and carbon show this property.

Malleability - Non-metals are non-malleable. If solids, they are brittle i.e. they break or shatter on hammering. For example, coal, sulphur, phosphorus are brittle.

Ductility – Non-metals cannot be drawn into thin wires. So they are not ductile.

Hardness – Non-metals are usually not hard. They are soft. For example, coal, sulphur and phosphorus are soft. Diamond is an exception to this. It is the hardest substance known.
Sonority - Non-metals are not sonorous, i.e. they do not produce a typical sound any being hit.

Conduction - Non- metals are usually poor conductors of heat and electricity. However, carbon in the form of gas carbon and graphite is an exception to this. These forms of carbon are good conductors of electricity.

Density – Non- metals which are gases have low density. Solid non-metals have low to moderate density. They are medium light. For example, sulphur, phosphorus and boron have densities of 1.82, 2.07 and 2.34 respectively. However, diamond has a high density which is about 3.5.

Melting and boiling point – Non-metals usually have low melting and boiling points. For example, phosphorus, sulphur, and iodine have melting points 440, 1150 and 1140 C respectively and boiling points 2800, 4450 and 1840C respectively. However, carbon, silicon and boron possess very high melting and boiling points.

Tensile strength – Non-metals have low tensile strength i.e. they have no tenacity.