Q1. Who discovered the electron?
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Answer: D. J. J. Thomson
J. J. Thomson discovered the electron through cathode ray experiments.
Chemistry - Atomic Structure Questions for SSC CGL (with Answers)
10 Chemistry - Atomic Structure MCQs from the General Awareness section, with answers and short explanations.
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Q2. What is the electronic configuration of sodium (atomic number 11)?
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Answer: C. 2, 8, 1
11 electrons fill as K = 2, L = 8, M = 1.
Q3. Isotopes of an element have:
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Answer: C. The same atomic number but different mass numbers
Isotopes have the same number of protons (atomic number) but different numbers of neutrons, so different mass numbers.
Q4. The neutron was discovered by:
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Answer: A. James Chadwick
James Chadwick discovered the neutron in 1932.
Q5. Rutherford's alpha-particle scattering (gold foil) experiment led to the discovery of the:
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Answer: A. Nucleus
The rebound of a few alpha particles showed a tiny, dense, positively charged nucleus.
Q6. Which subatomic particle carries no electric charge?
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Answer: D. Neutron
The neutron is electrically neutral.
Q7. Which isotope of hydrogen has no neutron in its nucleus?
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Answer: B. Protium
Protium (¹H) has one proton and no neutron.
Q8. How many neutrons are present in a sodium atom with mass number 23 and atomic number 11?
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Answer: C. 12
23 - 11 = 12 neutrons.
Q9. An element has the electronic configuration 2, 8, 7. What is its valency?
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Answer: A. 1
It needs one more electron to reach 8, so its valency is 1 (this is chlorine).
Q10. An isotope of which element is used in the treatment of goitre?
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Answer: B. Iodine
A radioactive isotope of iodine is used in treating goitre, a thyroid condition.
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