Concept check—pick the wrong statement about basic nuclear/particle facts (only one statement below is incorrect). Which one is it?
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AThe nucleus of a hydrogen atom (protium) is identical with a proton.
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BA beta (β−) ray particle is identical with an electron.
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CThe mass of an electron is about 1/1800th of the mass of the lightest nucleus (proton).
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DA positron is heavier than a proton.
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EAn alpha particle is a helium nucleus containing two protons and two neutrons.
Answer
Correct Answer: A positron is heavier than a proton.
Explanation
Introduction / Context:Many entry-level nuclear questions test whether you can separate accurate facts from plausible-sounding misconceptions. Electrons, positrons, protons, and alpha particles have well-established identities and masses that should be memorized for quick elimination logic in multiple-choice items.
Given Data / Assumptions:
- Protium (ordinary hydrogen) has a nucleus consisting of a single proton.
- β− radiation consists of high-energy electrons emitted in nuclear decay.
- The electron-to-proton mass ratio is roughly 1/1836 (≈ 1/1800 by rough GK).
- Positron has the same mass as an electron but positive charge.
Concept / Approach:Evaluate each statement against standard constants and identities. A positron (e+) is the electron’s antiparticle; its mass is identical to the electron’s, far lighter than a proton. Therefore, any statement claiming a positron is heavier than a proton is false. The other statements align with standard definitions: β− equals an electron; protium’s nucleus is a proton; and the widely used rounded mass ratio is acceptable. An alpha particle is indeed a helium-4 nucleus (2p + 2n).
Step-by-Step Solution:Check Statement A: true for 1H1 (protium).Check Statement B: β− is an electron → true.Check Statement C: 1/1800 is a rounded figure close to 1/1836 → acceptable.Check Statement D: positron mass = electron mass ≪ proton mass → false.Check Statement E: alpha = 2p + 2n → true.
Verification / Alternative check:Reference mass values: m_e ≈ 9.11e−31 kg, m_p ≈ 1.67e−27 kg (≈ 1836 m_e). Positron mass equals m_e; therefore it cannot be heavier than a proton.
Why Other Options Are Wrong:A/B/C/E are consistent with textbook definitions and accepted constants.D contradicts the equality m_e = m_positron and the much larger proton mass.
Common Pitfalls:Mixing up “antiparticle” with “heavier partner”; antiparticles mirror charge and certain quantum numbers, not mass magnitude relative to the corresponding particle.
Final Answer:A positron is heavier than a proton.