NEET NEET SOLVED PAPER 2015 (C)

  • question_answer
                   Magnetic moment 2.84 BM is given by (At. no. \[Ni=28,\,Ti=22,\,Cr=24,\,Co=27\])           

    A)  \[N{{i}^{2+}}\] 

    B)  \[T{{i}^{3+}}\]                  

    C)  \[C{{r}^{3+}}\] 

    D)  \[C{{O}^{2+}}\]

    Correct Answer: A

    Solution :

    Magnetic moment, \[\mu =\sqrt{n(n+2)}\]BM where, n = number of unpaired electrons \[\mu =2.84(given)\]                 \[\therefore \]  \[284=\sqrt{n(n+2)}B.M\]                                 \[{{(2.84)}^{2}}=n(n+2)\]                                 \[8={{n}^{2}}+2n\]                 \[{{n}^{2}}+2n-8=0\]                 \[{{n}^{2}}+4n-2n-8=0\]                 \[n(n+4)-2(n+4)=0\]                                                 \[n=2\] \[N{{i}^{2+}}=[Ar]3{{d}^{8}}4{{s}^{0}}\](two unpaired electrons) \[T{{i}^{3+}}=[Ar]3{{d}^{1}}4{{s}^{0}}\] (one unpaired electrons) \[C{{r}^{3+}}=[Ar]3{{d}^{3}}\], (three unpaired electrons) \[C{{o}^{2+}}=[Ar],3{{d}^{7}},4{{s}^{0}}\](three unpaired  electrons) So, only \[N{{i}^{2+}}\] has 2 unpaired electrons.


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