CAIE A-Level Chemistry 28.1.4 Variable Oxidation States

Practise explaining variable oxidation states through the similar energies of the 3d and 4s subshells.

Exam points

state that the occupied 3d and 4s subshells are close or similar in energy
explain that different numbers of 3d and 4s electrons can therefore be removed or used in bonding
link this electron participation to formation of several stable oxidation states such as Fe2+ and Fe3+

[Maximum number: 1]

$\mathrm{Fe}^{2+}$ ions can be oxidised to $\mathrm{Fe}^{3+}$ ions under alkaline conditions by suitable oxidising agents.

Iron is a transition element. Explain why iron forms stable compounds in both the +2 and the +3 oxidation states.

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