JEE Main & Advanced Sample Paper JEE Main - Mock Test - 16

  • question_answer
    Atomic number of \[Cr\] and \[Fe\]are respectively 25 and 26, which of the following is paramagnetic?

    A) \[[Cr{{(CO)}_{6}}]\]          

    B)       \[[Fe{{(CO)}_{5}}]\]

    C) \[{{[Fe{{(CO)}_{6}}]}^{4-}}\]        

    D)       \[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

    Correct Answer: D

    Solution :

    \[C{{r}^{3+}}\] has \[4s{}^\circ 3{{d}^{3}}\] electronic configuration with 3 unpaired electrons, hence paramagnetic. In other cases pairing of d-electrons take place in presence of strong field ligands such as \[CO\]or\[C{{N}^{-}}\]. In \[Cr{{(CO)}_{6}}\] molecule 12 electrons are contributed by \[CO\]group and it contain no odd electron


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