Isotopes and IsobarsPractice Questions & MCQs
Practice Isotopes and Isobars questions from Atomic Foundations of Matter (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.
Isotopes and IsobarsQuiz - Solve & Score
Q1. Why is the atomic mass of chlorine about 35.5, not a whole number?
- A.it is the average mass of its isotopes in their natural proportions
- B.chlorine has half a proton
- C.chlorine atoms are unstable
- D.electrons add 0.5 to the mass
Answer: A. it is the average mass of its isotopes in their natural proportions
Q2. Which property would be the SAME for two isotopes of the same element?
- A.the way they react chemically
- B.their mass
- C.their number of neutrons
- D.their density
Answer: A. the way they react chemically
NCERT fact (chemistry, chapter 'Journey Inside the Atom'): Isotopes have the same atomic number Z but different mass number A, since A = protons + neutrons; comparing the given pair => only the neutron count differs while the chemistry is identical; hence the chosen option = the way they react chemically. Why option A fits - Correct. Distractor analysis: option B) 'their mass' is incorrect: Isotopes differ in mass; option C) 'their number of neutrons' doesn't hold - Isotopes differ in neutron number. Final answer - A) the way they react chemically.
Q3. Which statement correctly contrasts isotopes and isobars?
- A.isotopes: same Z, different A; isobars: same A, different Z
- B.isotopes: same A, different Z; isobars: same Z, different A
- C.both have the same Z and the same A
- D.both are always radioactive
Answer: A. isotopes: same Z, different A; isobars: same A, different Z
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