MCAT General Chemistry Question 247: Answer and Explanation
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Question: 247
1. An atom contains 29 hadrons comprised of two down quarks and one up quark and 28 hadrons comprised of two up quarks and one down quark. Which one of the following is the identity of the atom?
- A. Iron-57
- B. Nickel-57
- C. Copper-57
- D. Nickel-58
Correct Answer: B
Explanation:
B A hadron with two up quarks and one down quark is a charged nucleon or proton. Because the atom has 28 of these protons, it must be nickel, eliminating choices A and C. Furthermore, a hadron with two down quarks and one up quark is a neutron. The atom has 29 of these, so the atomic mass must be 28 + 29 = 57, eliminating choice D.