The spin-only magnetic moments of $\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$ and $\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}$ are nearly similar.
B
The gemstone, ruby, has $\mathrm{Cr}^{3+}$ ions occupying the octahedral sites of beryl.
C
The spin-only magnetic moment of $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_4\left(\mathrm{H}_2 \mathrm{O}\right)_2\right]^{2+}$ is 2.83 BM .
D
The color of $\left[\mathrm{CoCl}\left(\mathrm{NH}_3\right)_5\right]^{2+}$ is violet as it absorbs the yellow light.
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
Ruby is aluminium oxide $\left(\mathrm{Al}_2 \mathrm{O}_3\right)$ containing about $0.5-1 \% \mathrm{Cr}^{3+}$ ions which are randomly distributed in the position normally occupied by $\mathrm{Al}^{3+}$ ions.
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