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

  • question_answer
    How many protons, neutrons and electrons are contained in one atom of\[_{19}^{39}K\]?

    A)  \[19\] protons \[+\,\,20\] neutrons \[+\,\,19\] electrons  

    B)  \[19\] protons \[+\,\,20\] neutrons \[+\,\,20\] electrons

    C)  \[20\] protons \[+\,\,19\] neutrons \[+\,\,20\] electrons

    D)  \[20\] protons \[+\,\,20\] neutrons \[+\,\,19\] electrons

    Correct Answer: A

    Solution :

     \[_{19}^{30}K\]gives the mass number\[(A)=39\] Number of protons in a neutral atom\[(Z)=\] Number of electrons\[=19\]. No. of neutrons\[(N)=A-Z\]\[=39-19=20\]


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