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9th Class Science Structure of the Atom Question Bank Structure of the Atom

  • question_answer
    A neutral atom of an element has a nucleus with a nuclear charge \[13\] times and mass \[27\] times as that of hydrogen nucleus. What is the ratio of electrons to protons in its stable positively charged ion?

    A)  \[27:13\]                      

    B)  \[10:13\]  

    C)  \[20:24\]          

    D)         \[10:14\]

    Correct Answer: B

    Solution :

     Let the neutral atom of the element be X. Given, the nuclear charge of \[X\] is \[13\] times that of hydrogen nucleus. \[\Rightarrow \]Atomic number\[=13\] Mass of \[X\] is \[27\] times that of hydrogen nucleus \[\Rightarrow \]Mass number\[=27\]. Since\[_{13}^{27}X,\,\,EC=2,\,\,8,\,\,3\] If \[X\] forms a stable, positively charged ion, i.e. \[{{X}^{+3}}\](as it has \[3\] valence electrons in its valence shell) \[{{X}^{+3}}\to \]Atomic number\[=13-3=10\].This implies that the number of electrons\[=10\]. Number of protons\[=13\]. Ratio\[=10:13\]or\[20:26\].


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