MCAT General Chemistry Question 249: Answer and Explanation
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Question: 249
3. A scientist in a laboratory observes a nucleon composed of three quarks with charges of +2/3 e, -1/3 e, and -1/3 e respectively. Which of the following best describes the nucleon?
- A. The particle is a neutron and it contains two down quarks.
- B. The particle is a proton and it contains two down quarks.
- C. The particle is a neutron and it contains one down quark.
- D. The particle is a proton and it contains one down quark.
Correct Answer: A
Explanation:
A The charges of the three quarks add up to 0, so the nucleon must be an uncharged neutron, eliminating choices B and D. The passage states that uncharged nucleons have two down quarks, eliminating choice C.