1 Ni2 cation is green but Zn2 cation is colorless explain 2

1) Ni^2 cation is green, but Zn^2 cation is colorless explain.

2) calculate the crystal field splitting energy in Kj/mol for blue soloution containing the copper complex [Cu(NH3)6]^2. the solution exhibits an absorpion max at 615nm

Solution

1) ni2+ has vacant d orbital. 3d8 4s0... But zn2+ is completly filled. So no d-d transiton ocurs in it. Hence colourles.

2)Use the formula E=hc/λ, where h is Planck\'s constant, c is the speed of light, and λ is your wavelength in m.
E=[(6.626x10^-34)(2.9979x10^8)] / 6.15x10^-7
E=12.67X10^-19 J/ion
Divide your answer by 1000 to get it to kJ/ion
E=12.67X10^-22
Take the answer from this and multiply it by Avogadro\'s constant which is 6.022x10^23 mol^-1

Final answer: 762.98kJ/mol.