Question

Which of the elements forms a colourless ion (Fe/ Cu / Cr / Na)​

Answer 1

In these following options, Cu and Na form colourless ions.

• Cu ions are colourless because of the absence of unpaired electrons in their 3d sub-shell.
• An electron moves to a higher energy orbital to absorb visible light. In an aqueous solution, Na ions are doesnot show any colour because of no absorption of visible light.