In ruby and emerald, the metal ion(s) present is/are
In ruby and emerald, the metal ion(s) present is/are
$\mathrm{Cr}^{6+}, \mathrm{Mn}^{3+}$
$\mathrm{Cr}^{3+}$
$\mathrm{Mn}^{3+}, \mathrm{Co}^{3+}$
$\mathrm{Co}^{3+}$
Solution
Ruby is $\mathrm{Al}_2 \mathrm{O}_3$ in which red colour is obtained when $\mathrm{Cr}^{3+}$ replaces $\mathrm{Al}^{3+}$ ions in octahedral sites. Emerald is $\mathrm{Be}_3 \mathrm{Al}_2\left(\mathrm{SiO}_3\right)_6$ in which green colour is obtained when $\mathrm{Cr}^{3+}$ replaces $\mathrm{Al}^{3+}$.