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Transition metals for AQA A-level Chemistry

Transition metals

This page covers the following topics:

1. Transition metal complexes
2. Coloured ions of transition metals
3. Variable oxidation states of transition metals
4. Transition metals as catalysts

Transition metals, Ti โ†’ Cu, have special properties because they have incomplete d-electron sub-shells. This allows them to form complexes consisting of a central metal atom surrounded by several ligands. These ligands can either be mono- or multidentate.

Transition metal complexes

Some transition metals are brightly coloured due to the unique spacing between their d sub-levels. The d-electrons absorb certain wavelengths of light and are moved up to an excited state, the remaining wavelengths of visible light are reflected and seen as colour.

Coloured ions of transition metals

Transition metals are special as they have variable oxidation states, allowing them to form multiple stable ions. The free, neutral form of each transition metal has an oxidation state of 0 [Scโ‚โ‚…โ‚Ž = Scโฐ]. For ions, the oxidation state is the same number as the charge [Vยณโบ= V''']. The oxidation state of a transition metal in a complex can be calculated by subtracting the charges of the individual atoms from the overall charge of the complex [TiClโ‚„ = Tiหกโฑฝ].

Variable oxidation states of transition metals

Their ability to form multiple stable oxidation states make transition metals very useful as catalysts. Transition metal catalysts are divided into two types, heterogeneous and homogenous, depending on whether they share the same phase as the reacting substances

Transition metals as catalysts

1

What is the wavelength range of visible light?

400-700 nm

What is the wavelength range of visible light?

2

Vโ‚‚Oโ‚… is used as a heterogeneous catalyst in the Contact process, to convert SOโ‚‚ to SOโ‚ƒ. Use a series of equations to show how this catalysis is achieved.

image

Vโ‚‚Oโ‚… is used as a heterogeneous catalyst in the Contact process, to convert SOโ‚‚ to SOโ‚ƒ. Use a series of equations to show how this catalysis is achieved.

3

What equation relates the energy difference between sub-levels to wavelength of light?

image

What equation relates the energy difference between sub-levels to wavelength of light?

4

What technique is used to determine the concentration of coloured ions in a solution?

colorimetry

What technique is used to determine the concentration of coloured ions in a solution?

5

Draw this complex, [Fe(Hโ‚‚O)โ‚ƒ(OH)โ‚ƒ].

image

Draw this complex, [Fe(Hโ‚‚O)โ‚ƒ(OH)โ‚ƒ].

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