Paper 3 · atomic structure / electron configuration

Which ion contains an unpaired electron?

Ca^{2+}

Cu^{2+}

K^+

Ti^{4+}

Explanation: The marking scheme gives answer B.

Cu^{2+}

has electron configuration [Ar]

3d^9

, which has one unpaired electron in the 3d subshell.

ZIMSEC Chemistry Paper 3, June 2009, Q5

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