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Electrons in Solids

Formula

    

Formal Mn
Oxidation
State

    

Number of
Unpaired
Electrons

Mn2O3

    

+3

    

4

MnO2

    

+4

    

3

KMnO4

    

+7

    

0

  • Overhead Projector Demonstration: How do we know there are electrons?

  • Mn2O3 => strongly paramagnetic, strongly attracted by magnet, capsule moves to the magnet.

  • MnO2 => moderately paramagnetic, moderately attracted by magnet, capsule gently rocked by magnet.

  • KMnO4 => diamagnetic, very weak repulsion by magnet, no effect on capsule.

  • Illustrates connection between oxidation numbers and numbers of unpaired electrons.

  • Samples are in gel-caps (or clear plastic straws, sealed with hot glue gun).

  • Show ferromagnetism with capsule filled with iron filings; much greater attraction, as capsule leaps to magnet.