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Wednesday, August 28, 2019

Why [Mn(H2O)6]+2 is colourless although in which Mn+2 ion had five unpaired electrons ?

There are 5 unpaired electrons in Mn+2 ion and we know that.
                                 Spin multiplicity is = (2S+1) 
                     Where S is some of spin thus  S = 5×1/2=5/2
                                            Hence multiplicity = (2S+1)= 6 

we know multiplicity of excited state cannot be six, thus electronic transition in Mn+2  are 
spin forbidden, hence [Mn(H2O)6]+2 salt appear colourless.

Also [Mn(H2O)6]+2 has centre of symmetry and in such cases electronic transition are expected to be laporate forbidden.

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