The number of neutrons in a nucleus of uranium 235, atomic number 92, is
Correct answer: B. 143
- A. 92
- B. 143
- C. 235
- D. 327
Explanation
Neutron number is mass number minus atomic number, so 235 minus 92 gives 143. The mass number counts protons and neutrons together, which are collectively called nucleons. Adding the two numbers, as in the 327 distractor, has no physical meaning.
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About Composition of Atomic Nuclei
Atomic nuclei contain positively charged protons and electrically neutral neutrons, collectively called nucleons. Questions use atomic number, mass number and nuclear notation to identify isotopes, isobars and isotones, and may connect nuclear composition with nuclear charge, mass defect, binding energy and the stability of the nucleus.
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