Question

Which of the following statement(s) is/are true regarding the Ruby gemstone?

• A. It contains 2% of $M{n}^{2+}$
• B. It contains 0.5-1% of $C{r}^{3+}$
• C. It shows colour due to d-d transitions
• D. It shows colour due to f-f transition

Answer 1

Answer: (B), (C)

It shows colour due to d-d transitions

Ruby is aluminium oxide $\left(A{l}_2{O}_3\right)$. It contains 0.5-1% of $C{r}^{3+}$ ions $\left(d^3\right)$. These ions are randomly distributed in the positions of $A{l}^{3+}$.
The colour shown by ruby is due to the $d-d$ transition in $C{r}^{3+}$.