Multiple choice Which of the following transition metal ions is expected to form colourless complexes? Mn2+ Fe3+ Zn2+ Ni2+ Reveal answer Fill a bubble to check yourself C Correct answer Explanation Zn: 3d10, 4s2 Zn2+: 3d10 In Zn2+, d-orbital is completely filled. So, it will form colourless complexes.