Class 9 · Science · Chemistry · Structure of the Atom

Discovery of Subatomic Particles (Electron, Proton, Neutron)Practice Questions & MCQs

Practice Discovery of Subatomic Particles (Electron, Proton, Neutron) questions from Structure of the Atom (Class 9 Science) - important MCQs with answers and step-by-step solutions. Solve the sample questions below, then practice the full set free on the RankByte app.

Discovery of Subatomic Particles (Electron, Proton, Neutron)Quiz - Solve & Score

  1. Q1. An atom turned into an ion by losing 12 electrons holds what charge in coulombs?

    • A.7.5*10^-19 C
    • B.1.6*10^-19 C
    • C.19.2*10^-19 C
    • D.19.2*10^-18 C

    Answer: C. 19.2*10^-19 C

    Each electron is 1.6*10^-19 C. Removing 12 electrons gives a net charge of 12 * 1.6*10^-19 = 19.2*10^-19 C.

  2. Q2. A pollen speck floating in air traps 50 electrons; what is the magnitude of its charge?

    • A.80*10^-18 C
    • B.31.25*10^-19 C
    • C.80*10^-19 C
    • D.1.6*10^-19 C

    Answer: C. 80*10^-19 C

    Each electron carries 1.6*10^-19 C. Total charge = 50 * 1.6*10^-19 = 80*10^-19 C.

  3. Q3. Robert Millikan balanced charged oil drops against gravity in his apparatus; what quantity did he determine?

    • A.the speed of cathode rays
    • B.the charge of a single electron
    • C.the mass of the nucleus
    • D.the number of atoms in a drop

    Answer: B. the charge of a single electron

    By balancing the electric force on oil drops against gravity, Millikan found the electron's charge, 1.6*10^-19 C.

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