The transition elements are metals. They have high melting points and densities, and are strong and hard. They form coloured compounds and act as catalysts.

Some properties of transition elements are different from those of the metals in group 1. Compared to other metals, most transition metals have:

**Remember point


Remember that these are typical properties – some transition metals may not show one or more of them. For example, mercury melts at just -39°C, so it is a liquid at room temperature.

The table shows the melting point and density of some transition elements, compared to three metals in the periodic table that are not transition elements.

The transition metals do not show trends in group properties, unlike group 1 and group 7, which do show trends.

Transition metals have similar properties, and some of these properties are different from those of the metals in group 1.

The transition metals have the following physical properties in common:

1. Compare the properties of sodium and chromium. How does the data show that chromium is a typical transition element, and sodium is a typical group 1 metal?

Chromium has a much higher melting point than sodium. The density of chromium is also greater than sodium. Most transition elements have high melting points and densities, so chromium is a typical transition element. The group 1 elements have low melting points and densities, so sodium is a typical group 1 element.

Chemical reactions

Reactions with oxygen

The group 1 elements react quickly with oxygen in the air at room temperature. Most transition elements react slowly, or not at all, with oxygen at room temperature. Some transition metals react with oxygen on heating, for example:

copper + oxygen → copper oxide

2Cu(s) + O₂(g) → 2CuO(s)

Reactions with water

The group 1 elements react vigorously with cold water. Most transition elements react slowly with cold water, or not at all.

Iron reacts with water and oxygen at room temperature to form hydrated iron(III) oxide, or rust.

For more information on rusting, visit the Using materials study guide.

Reactions with halogens

The group 1 elements react vigorously with the halogens. Some transition elements also react with halogens, for example:

iron + chlorine → iron(III) chloride

Fe(s) + Cl₂(g) → FeCl₃(s)

Coloured compounds
Metals that are not transition elements usually form white compounds. Transition elements form coloured compounds.

The table shows the colours of some iron compounds.

CompoundColourIron(II) hydroxide, Fe(OH)₂ | Pale green
Iron(III) hydroxide, Fe(OH)₃ | Orange-brown
Iron(III) oxide, Fe₂O₃ | Red-brown

Catalytic activity

Catalysts are substances that increase the rate of reaction without being used up in the reaction. For example: