# Transition metals have characteristic properties that distinguish them from other metals, such as those in Group 1. Explain why transition metals are able to form ions with different oxidation states, and describe how this property makes them useful as catalysts.

> Edexcel A-Level Chemistry (9CH0) — 15.1 Transition metal chemistry · Explain · 5 marks

> Manganese is a transition metal used in the manufacture of steel and in certain industrial chemical processes. It can form ions including Mn²⁺, Mn³⁺, and Mn⁴⁺.

## Mark scheme (5 marks)

1. Transition metals have incompletely filled d sub-levels (d orbitals) / d electrons can be lost or gained
2. The energy levels of the d orbitals are close together / similar in energy, so different numbers of electrons can be removed
3. This means transition metal ions can change oxidation state during a reaction / switch between different ions (e.g. Mn²⁺ and Mn³⁺)
4. As a catalyst, the transition metal ion accepts electrons from (or donates electrons to) reactants / provides an alternative reaction pathway
5. The transition metal ion is regenerated at the end of the reaction / returns to its original oxidation state, so it is not used up

## Key terms

- [transition metal](https://www.gradenine.co.uk/glossary/transition-metal)
- [oxidation state](https://www.gradenine.co.uk/glossary/oxidation-state)
- [catalyst](https://www.gradenine.co.uk/glossary/catalyst)

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- [Revision notes for Edexcel A-Level Chemistry (9CH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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