Question

The correct order for the wavelength of absorption in the visible region is:
A.\[{[Ni{(N{O_2})_6}]^{4 - }} < {[Ni{(N{H_3})_6}]^{2 + }} < {[Ni{({H_2}O)_6}]^{2 + }}\]
B.\[{[Ni{(N{O_2})_6}]^{4 - }} < {[Ni{({H_2}O)_6}]^{2 + }} < {[Ni{(N{H_3})_6}]^{2 + }}\]
C.\[{[Ni{({H_2}O)_6}]^{2 + }} < {[Ni{(N{H_3})_6}]^{2 + }} < {[Ni{(N{O_2})_6}]^{4 - }}\]
D.\[{[Ni{(N{H_3})_6}]^{2 + }} < {[Ni{({H_2}O)_6}]^{2 + }} < {[Ni{(N{O_2})_6}]^{4 - }}\]

Answer 1

Hint: The wavelength of absorption in the visible region depends on the central metal ion and ligands. And if the central metal is the same it depends on the CFSE value of the ligand in the spectrochemical series.

Complete step by step answer:
The central metal ions in all the three complexes are exactly the same. So, the absorption in the visible region depends on the ligands. So, mainly we need to focus on the ligands which are present in the mentioned questions. So, the order in which CFSE values of the ligands increase in the spectrochemical series is as follows: ${H_2}O < N{H_3} < N{O_2}$. So, to proceed with these types of questions we need to focus on the arrangement of complex compounds which are present in the question and also we need to check the ligands which are given in the question. Moreover, we need to also remember the spectrochemical series.
The correct answer of the above question is option (A) that is\[{[Ni{(N{O_2})_6}]^{4 - }} < {[Ni{(N{H_3})_6}]^{2 + }} < {[Ni{({H_2}O)_6}]^{2 + }}\].

Additional information:
The spectrochemical series is the most efficient way to organize Ligands by field strength. Ligands affect the electrons of the metals, splitting degenerate energy levels into more organized levels of energy.
Wavelength is the distance between two successive crests and troughs of a wave and it is measured in the direction of the wave.


Note:
Ligands are ions which are used to bind the central metal atom to form a coordination complex. The bonding with the metal generally involves a donation of one or more than one Ligand’s electron pair.
There are mainly two types of Ligands: A) Anionic Ligands B) Neutral Ligands.
Examples of Anionic Ligands are: ${F^ - },B{r^ - },C{l^ - }$ . . . . etc .
Examples of Neutral Ligands are: $NO,CO,{H_2}O$ . . . .etc .