Transition metals - AQAChemical properties of transition elements
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.
There are differences in the chemical propertiesA description of how a substance reacts with other substances. For example, flammability, pH, reaction with acid, etc. of metals in group 1The first vertical column of elements in the periodic table, starting with lithium and ending with francium. Also called the alkali metals. and the transition elementA metal that is located in between groups 2 and 3 of the periodic table and has coloured compounds..
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)
Ions with different charges
Transition elements form ionElectrically charged particle, formed when an atom or molecule gains or loses electrons. with different charges. For example:
manganese forms Mn2+ and Mn3+ ions
copper forms Cu+ and Cu2+ ions
Coloured compounds
Metals that are not transition elements usually form white compoundA substance formed by the chemical union of two or more elements.. Transition elements form coloured compounds.
The table shows the colours of some iron compounds.
Compound
Colour
Iron(II) hydroxide, Fe(OH)2
Pale green
Iron(III) hydroxide, Fe(OH)3
Orange-brown
Iron(III) oxide, Fe2O3
Red-brown
Compound
Iron(II) hydroxide, Fe(OH)2
Colour
Pale green
Compound
Iron(III) hydroxide, Fe(OH)3
Colour
Orange-brown
Compound
Iron(III) oxide, Fe2O3
Colour
Red-brown
Catalytic activity
catalystA substance that changes the rate of a chemical reaction without being changed by the reaction itself. are substances that increase the rate of reactionA measurement of how quickly a reaction takes place. without being used up in the reaction. For example:
iron is the catalyst in the Haber processThe industrial chemical process that makes ammonia by reacting nitrogen and hydrogen together., which makes ammonia
manganese(IV) oxide increases the decomposition of hydrogen peroxide to oxygen and water
