Structure of Atom – Multiple Choice Questions (MCQs)

1. 1. Who discovered the electron?

   • A. J.J. Thomson
   • B. Ernest Rutherford
   • C. James Chadwick
   • D. Niels Bohr

2. 2. The mass of a proton is approximately equal to the mass of a/an:

   • A. Neutron
   • B. Electron
   • C. Alpha particle
   • D. Deuteron

3. 3. Which of the following subatomic particles has a negative charge?

   • A. Electron
   • B. Proton
   • C. Neutron
   • D. Photon

4. 4. The atomic number (Z) of an element is equal to the number of:

   • A. Protons
   • B. Neutrons
   • C. Electrons
   • D. Protons + Neutrons

5. 5. Isotopes are atoms of the same element having:

   • A. Same atomic number but different mass numbers
   • B. Different atomic number but same mass number
   • C. Same number of neutrons
   • D. Different number of electrons

6. 6. Isobars are atoms having:

   • A. Same mass number but different atomic numbers
   • B. Same atomic number but different mass numbers
   • C. Same number of neutrons
   • D. Different number of electrons

7. 7. The dual nature of matter was proposed by:

   • A. Louis de Broglie
   • B. Werner Heisenberg
   • C. Erwin Schrödinger
   • D. Max Planck

8. 8. Heisenberg's Uncertainty Principle states that:

   • A. It is impossible to determine simultaneously the exact position and exact momentum of an electron
   • B. Electrons move in fixed orbits
   • C. Energy is quantized
   • D. Light has dual nature

9. 9. The principal quantum number (n) describes the:

   • A. Size and energy of the orbit
   • B. Shape of the orbit
   • C. Orientation of the orbit
   • D. Spin of the electron

10. 10. The azimuthal quantum number (l) describes the:

    • A. Shape of the orbital
    • B. Size of the orbital
    • C. Orientation of the orbital
    • D. Spin of the electron

11. 11. The magnetic quantum number (ml) describes the:

    • A. Orientation of the orbital
    • B. Shape of the orbital
    • C. Size of the orbital
    • D. Spin of the electron

12. 12. The spin quantum number (ms) describes the:

    • A. Spin orientation of the electron
    • B. Shape of the orbital
    • C. Size of the orbital
    • D. Orientation of the orbital