Transition Elements (Cambridge (CIE) O Level Chemistry): Revision Note

Transition Elements

General properties of the transition elements

• They are very hard and strong metals and are good conductors of heat and electricity

• They have very high melting points and are highly dense metals

• For example, the melting point of titanium is 1,668 °C whereas potassium in Group I melts at only 63.5 °C, slightly warmer than the average cup of hot chocolate!

• The transition elements form coloured compounds and often have more than one oxidation state, such as iron readily forming compounds of both Fe²⁺ and Fe³⁺

• These coloured compounds are responsible for the pigments in many paints and the colours of gemstones and rocks

• Transition elements, as elements or in compounds, are often used as catalysts to improve the rate of reaction in industrial processes

  • Transition element catalysts of platinum or rhodium are also used in car exhausts in the 'catalytic converter' to reduce the levels of nitrogen oxides and carbon monoxide produced

The transition elements on the Periodic Table

• The transition elements have more than one oxidation number, as they can lose a different number of electrons, depending on the chemical environment they are in

• For example, iron either:

  • Loses two electrons to form Fe²⁺ so has an oxidation number of +2

  • Loses three electrons to form Fe³⁺ so has an oxidation number of +3

• Compounds containing transition elements in different oxidation states will have different properties and colours

  • For example, in solution Fe²⁺ ions are pale green, Fe³⁺ ions are brown and Cu²⁺ ions are pale blue

Ions of the same element can have different oxidation numbers forming different colours

 Uses of the transition elements

• The transition elements are used extensively as catalysts due to their ability to interchange between a range of oxidation states

• This allows them to form complexes with reagents which can easily donate and accept electrons from other chemical species within a reaction system

• They are used in medicine and surgical applications such as limb and joint replacement (titanium is often used for this as it can bond with bones due to its high biocompatibility)

• They are also used to form coloured compounds in dyes and paints, stained glass and jewellery