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10th Class Science Periodic Classification of Elements Question Bank Periodic Classification of Elements

  • question_answer
    Three elements P, Q, R form a Dobereiner triad. The atomic weights of P and R are 35 and 127 respectively. Find the atomic weight of Q.                         

    A) 40                                         

    B) 60           

    C) 81                                         

    D) 120

    Correct Answer: C

    Solution :

    The three elements P, Q and Rare halogens \[Cl,Br\] and I as per the given atomic weights. The atomic weight of Q is given by the mean of the first and the third elements as given below.                 \[\frac{35+127}{2}=\frac{162}{2}=81\](Bromine)


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