The transition metal ions responsible for color in ruby and emerald are, respectively :

Options

A. `Co^(3+) " and " Cr^(3+)`
B. `CO^(3+) and CO^(3+)`
C. `Cr^(3+) " and "Cr^(3+)`
D. `Cr^(3+) and CO^(3-)`

Answer

C

Explanation

A ruby is crystal of alumina, aluminum oxide `(Al_2O_3)`
containing a trace of chromium (III) ions replacing some of the aluminum ions.In ruby each `Al^(3+)` ion and `Cr^(3+)` ion is surronded by six oxide ions is an octahedral arrangment. The origin of the color of emeralds is similar to that of the color of rubies. However. the bulk of an emerald crystal is composed of beryl. beryllium aluminum silicate `(Be_3, Al_2 (SiO_3)_6)` instead of the alumina which form rules. The color of rubies. The color is produced by chromium (III)ions, which replace some of the aluminum ions in the crystal. In emeralds, the `Cr^(3+)` is surounded by six silicate ions, rather than the six oxide ions is ruby. Therefore , the color (green ) of emetalds is different from that of ruby.