Which colour is developed to the solution when alkaline earth metals are dissolved in liquid ammonia?
Show Hint
Differentiate between groups: Alkali metal solutions in liquid ammonia are initially deep blue (and turn bronze at very high concentrations). Alkaline earth metal solutions are uniquely deep blue-black.
Step 1: Understanding the Concept:
Alkaline earth metals (Group 2) dissolve in liquid ammonia to form ammoniated cations and ammoniated electrons. Step 2: Formula Application:
$M + (x+y)NH_3 \rightarrow [M(NH_3)_x]^{2+} + 2[e(NH_3)_y]^-$. Step 3: Explanation:
The presence of solvated (ammoniated) electrons absorbs energy in the visible region of light. For alkaline earth metals, these solutions are typically very dark, described as deep blue-black or bronze (when concentrated). This is similar to alkali metals, which produce a characteristic deep blue color in dilute solutions. Step 4: Final Answer:
The color developed is Deep blue black.