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Chemistry Chapter 3 : Topic 15
Radioactive Isotopes
1 / 20
Atoms of the same element may have identical chemical properties but different nuclear stability due to variation in the number of neutrons. Such atoms are called isotopes. Which statement correctly explains why some isotopes are radioactive while others are stable?
Reasoning: Nuclear stability is mainly determined by the neutron-to-proton ratio. An imbalance leads to instability and radioactivity.
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Carbon has isotopes like Carbon-12, Carbon-13, and Carbon-14. Carbon-14 is radioactive while others are stable. What is the best explanation?
Reasoning: Carbon-14 has extra neutrons, causing nuclear instability and radioactive decay.
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Which statement best defines radioactive isotopes?
Reasoning: Radioactive isotopes are unstable isotopes that spontaneously decay and emit radiation.
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A student states: “All isotopes of an element behave identically in chemical reactions but may differ in nuclear behavior.” This statement is correct because:
Reasoning: Chemical properties depend on electron configuration, while nuclear stability depends on neutrons.
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Which of the following isotopes is commonly used in medical diagnosis due to its radioactive nature?
Reasoning: Iodine-131 is a radioactive isotope used in medical imaging and treatment.
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If an isotope is radioactive, it means that its nucleus:
Reasoning: Radioactive isotopes release energy in the form of radiation to achieve stability.
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Which condition most likely leads to radioactivity in isotopes?
Reasoning: Imbalanced neutron-to-proton ratio causes nuclear instability.
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A nucleus emits radiation spontaneously. What does this indicate about the isotope?
Reasoning: Radioactivity is a nuclear process, not chemical; it involves nuclear transformation.
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Which statement about isotopes is INCORRECT?
Reasoning: Isotopes may differ in stability; some are radioactive.
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Carbon dating uses radioactive Carbon-14 because:
Reasoning: Carbon-14 decays at a constant known rate, allowing age estimation of fossils.
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Which particle emission is commonly associated with radioactive isotopes?
Reasoning: Radioactive decay involves emission of alpha, beta, or gamma radiation.
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Two isotopes of chlorine exist: Cl-35 and Cl-37. Both are stable. This shows that:
Reasoning: Stability depends on nuclear structure, not just isotope existence.
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Which best explains why radioactive isotopes are useful in cancer treatment?
Reasoning: Radiation from radioactive isotopes damages cancerous cells.
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A radioactive isotope gradually changes into another element. This process is called:
Reasoning: Radioactive decay changes the nucleus, forming a different element.
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Which statement correctly distinguishes stable and radioactive isotopes?
Reasoning: Radioactivity originates from unstable nuclei.
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Why do isotopes of the same element show similar chemical behavior?
Reasoning: Chemical properties depend on electron configuration, which is the same in isotopes.
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Which isotope is MOST likely to be radioactive?
Reasoning: Excess neutrons make the nucleus unstable, leading to radioactivity.
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Radioactivity is best described as:
Reasoning: Radioactivity originates from the nucleus and involves emission of radiation.
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If a stable isotope is compared with a radioactive isotope of the same element, the key difference lies in:
Reasoning: Stability differences are due to nuclear structure, not chemical properties.
20 / 20
Which conclusion is scientifically correct about isotopes?
Reasoning: Only some isotopes are unstable; these are radioactive.
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