Fill in the Blanks
1. The charge of an electron was determined by __________ oil drop experiment.
2. The charge on an electron is __________ C.
3. In Thomson's model, electrons are embedded in a sphere of __________ charge.
4. Thomson's atomic model is also called the __________ pudding model.
5. X-rays were discovered by __________.
6. The phenomenon in which elements emit radiations on their own is called __________.
7. α‐-particles are actually __________ nuclei.
8. In Rutherford's experiment, most α‐-particles passed through the gold foil because the atom is mostly __________.
9. The central positively charged part of atom is called the __________.
10. According to Rutherford's model, electrons revolve around the nucleus in fixed circular __________.
Short Questions
1. Who proposed the plum pudding model of atom?
2. What was the main aim of Millikan’s oil drop experiment?
3. What is the charge present on an electron?
4. Why is Thomson's model called the plum pudding model?
5. Who discovered X-rays?
6. What are α-particles?
7. What are β-rays?
8. What are γ-rays?
9. What did Rutherford conclude from α‐-particle scattering experiment?
10. What is nucleus?
11. Why did most α‐particles pass through the gold foil undeflected?
12. Why were a few α‐particles deflected?
13. What are the main postulates of Rutherford's atomic model?
14. What are the limitations of Rutherford's model?
15. Name the three fundamental particles.
MCQs
1. The charge of electron was determined by:
A) Rutherford
B) Millikan
C) Chadwick
D) Bohr
2. Thomson’s atomic model is also known as:
A) Nuclear model
B) Planetary model
C) Plum pudding model
D) Quantum model
3. The positively charged part of atom is called:
A) Electron
B) Orbit
C) Nucleus
D) Shell
4. X-rays were discovered by:
A) Rutherford
B) J. J. Thomson
C) Wilhelm Röntgen
D) Chadwick
5. α-particles are:
A) Electrons
B) Helium nuclei
C) Neutrons
D) Gamma rays
6. Most of the space inside an atom is:
A) Filled with electrons
B) Filled with protons
C) Empty
D) Filled with neutrons
7. The charge on proton is:
A) –1
B) 0
C) +1
D) +2
8. Which particle has no charge?
A) Electron
B) Proton
C) Neutron
D) Alpha particle
9. In Rutherford’s experiment, a few α-particles were deflected because:
A) Atom is empty
B) Electrons attracted them
C) Positive charge is concentrated in nucleus
D) Gold foil absorbed them
10. Which radiation has maximum penetrating power?
A) α-rays
B) β-rays
C) γ-rays
D) Cathode rays
11. According to Rutherford’s model, electrons revolve around the nucleus in:
A) Waves
B) Circular orbits
C) Straight lines
D) Random paths
12. The approximate radius of nucleus is:
A) 10−10 m
B) 10−12 m
C) 10−15 m
D) 10−8 m
13. Radioactivity was discovered by:
A) Bohr
B) Henri Becquerel
C) Thomson
D) Dalton
14. Which particle is negatively charged?
A) Proton
B) Neutron
C) Electron
D) Alpha particle
15. Rutherford used which metal foil in his scattering experiment?
A) Silver
B) Copper
C) Platinum
D) Gold