9th class Chemistry, Chapter 2: Atomic Structure MCQs

1. How many electrons can be accommodated at the most in the third shell of the elements?

1. (A) 8
2. (B) 18 ✓
3. (C) 10
4. (D) 32

2. What information was obtained from discharge tube experiments?

1. (A) Structure of atom was discovered.
2. (B) Neutrons and protons were discovered.
3. (C) Electrons and protons were discovered. ✓
4. (D) Presence of nucleus in an atom was discovered.

3. Why have isotopes not been shown in the periodic table?

1. (A) Periodic table cannot accommodate a large number of isotopes of different elements.
2. (B) Some of the isotopes are unstable and they give rise to different elements
3. (C) All the isotopes have same atomic number; so there is no need to give them separate places. ✓
4. (D) Isotopes do not show periodic behavior.

4. Which particle is present in different number in the isotopes?

1. (A) Electron
2. (B) Neutron ✓
3. (C) Proton
4. (D) Both neutron and electron

5. In which isotope of oxygen there are the equal number of protons, electrons and neutrons?

1. (A) ¹⁷O
2. (B) ¹⁶O ✓
3. (C) ¹⁸O
4. (D) None of these

6. What will be the relative atomic mass of nitrogen given the abundances of its two isotopes, ¹⁴N and ¹⁵N are 99.64 and 0.35 respectively.

1. (A) 14.0210
2. (B) 14.0021 ✓
3. (C) 14.2100
4. (D) 14.1200

7. How is radiocarbon dating useful for archeologists?

1. (A) It helps determine the age of organic matter. ✓
2. (B) It helps determine the composition of matter.
3. (C) It helps determine the usefulness of matter.
4. (D) It helps determine whether the matter is radioactive or not.

8. What does keep the particles present in the nucleus intact?

1. (A) Particles are held together by strong nuclear force. ✓
2. (B) Particles are held together by weak nuclear force.
3. (C) Particles are held together by electrostatic force.
4. (D) Particles are held together by dipolar force.

9. How do electrons keep themselves away from the oppositely charged nucleus?

1. (A) By keeping themselves stationary
2. (B) By revolving around the nucleus ✓
3. (C) Due to their wave-like nature
4. (D) A magnetic field around the nucleus keeps them away

10. Rubidium consists of two isotopes ⁸⁵Rb and ⁸⁷Rb. The percent abundance of the light isotope is 72.2%. What is the percent abundance of the heavier isotope? Its atomic mass is 85.47

1. (A) 15%
2. (B) 27.8% ✓
3. (C) 37%
4. (D) 72%

11. The idea of atom was first proposed in Greece by the philosopher:

1. (A) Democritus ✓
2. (B) Dalton
3. (C) Thomson
4. (D) Rutherford

12. Around 1800 the evidence for the existence of atoms was provided by the English chemist:

1. (A) J.J. Thomson
2. (B) E. Goldstein
3. (C) Niels Bohr
4. (D) John Dalton ✓

13. A proton is heavier than an electron by about:

1. (A) 18 times
2. (B) 1836 times ✓
3. (C) 1000 times
4. (D) 100 times

14. Cathode rays bend towards the positively charged plate, which shows that they carry:

1. (A) Positive charge
2. (B) No charge
3. (C) Both charges
4. (D) Negative charge ✓

15. The properties of cathode rays were studied in 1897 by:

1. (A) Chadwick
2. (B) Rutherford
3. (C) J.J. Thomson ✓
4. (D) E. Goldstein

16. Canal rays (anode rays) were discovered in 1886 by:

1. (A) John Dalton
2. (B) E. Goldstein ✓
3. (C) J.J. Thomson
4. (D) Niels Bohr

17. Goldstein used a discharge tube having a:

1. (A) Magnet inside it
2. (B) Perforated cathode ✓
3. (C) Perforated anode
4. (D) Gold foil

18. The neutron was discovered in:

1. (A) 1911
2. (B) 1933 ✓
3. (C) 1897
4. (D) 1886

19. The atom which does not have a neutron is:

1. (A) Helium (⁴₂He)
2. (B) Carbon (¹²₆C)
3. (C) Ordinary hydrogen (¹₁H) ✓
4. (D) Deuterium (²₁H)

20. In 1911 Rutherford discovered the nucleus by hitting a stream of special particles on a thin:

1. (A) Gold foil ✓
2. (B) Silver foil
3. (C) Copper plate
4. (D) Aluminium sheet