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Coordination Compounds

Question
CBSEENCH12011302
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which of the following complex ions is expected to absorb visible light?

(At. no.Zn = 30, Sc = 21, Ti = 22, Cr = 24)

  • [Sc(H2O)(NH3)3]3+

  • [Ti(en)2(NH3)2]4+

  • [Cr(NH3)6]3+

  • [Zn(NH3)6]2+

Solution

D.

[Zn(NH3)6]2+

only those transition metal complexes are expected to absorb visible light, in which d-subshell is incomplete (ie, has unpaired electron) and excitation of an electron from a lower energy orbital to higher energy orbital is possible.
a) In [Sc(H2O)(NH3)3]3+ Sc is present in Sc3+ = [Ar]3d0,4s0
 since in this complex excitation of the electron is not possible, it will not absorb visible light.
b) In [Ti(en)2(NH3)2]4+,Ti  is present as Ti4+. 
Ti4+ = [Ar] 3d0,4s0
Hence it will not absorb visible light.
c) In [Cr(NH3)6]3+ ,Cr is present as Cr3+
Cr3+ = [Ar]3d3,4s0
Since this complex has three unpaired electrons, excitation of electrons is possible and thus, it is expected that this complex will absorb visible light.
d) In [Zn(NH3)6]2+, Zn is present Zn2+
Zn2+ = [Ar] 3d10, 4s0
Hence, this complex will not absorb visible light. 

Some More Questions From Coordination Compounds Chapter

Write the formula for the following coordination compound:
Tris(ethane -1, 2-diamine) chromium(III) chloride

Write the formula for the following coordination compound:
Amminebromidochloridonitrito-N-platinate (II)

Write the formula for the following coordination compound:
Dichloridobis(ethane-1, 2-diamine)platinum(lV) nitrate.

Write the formula for the following coordination compound:
Iron(III) hexacyanidoferrate(II)

Write the IUPAC names of the following coordination compounds:
(i) [Co(NH3)6]Cl3
(ii) [Co(NH3)5Cl]Cl2
(iii) K3[Fe(CN)6]
(iv) K3[Fe(C2O4)3]
(v) K2[PdCl4]
(vi) [Pt(NH3)2Cl(NH2CH3)]Cl.

Indicate the type of isomerism exhibited by the following complexes and draw structures for these isomers:
(i)    K[Cr(H2O)2(C2O4)2],                      (ii) [Co(en)3Cl3,
(iii) [Co(NH3)5(NO2)]|NO3]2,                 (iv) [Pt(NH3)(H2O)Cl2]

Explain on the basis of valence bond theory that [Ni(CN)4]2–  ion with square planar is diamagnetic and the [NiCl4]2– ion with tetrahedral geometry is paramagnetic.

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