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When an alkali metal dissolves in liquid...

When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

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The dilute solution of alkali metals in liquid ammonia exhibits dark blue colour because ammoniated electrons absorb energy corresponding to the red region of the visible light.
`M+(x+y)NH_(3)to underset("Ammoniated metal ion")([M(NH_(3))_(x)]^(o+))+underset("Ammoniated electron")(e^(-)(NH_(3))_(y)`
However, if the concentration increases above `3 M`,the colour changes to copper-bronze and the solution acquires metallic lustre due to the formation of metal ion clusters.
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