Question detail
An atom has a mass number of 40 and an atomic number of 18. Determine the number of neutrons in this atom. Use the shielding choice context to keep Mass number, atomic number and isotopes distinct from nearby atomic and nuclear radiation ideas.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Atoms and isotopes
Question
- A. 22 (mass number atomic number and)
- B. 18 (mass number atomic number and)
- C. 40 (mass number atomic number and)
- D. 58 (mass number atomic number and)
Answer
The correct answer is 22 (mass number atomic number and).
Explanation
The correct answer is 22 (mass number atomic number and). It supports the learning objective: Calculate the number of neutrons using mass number minus atomic number.. The correct answer is 22 (mass number atomic number and). It directly supports the learning objective: Calculate the number of neutrons using mass number minus atomic number.. In Mass number, atomic number and isotopes, this is the best option because it matches the specific shielding choice context; the other options mix up nearby ideas such as activity, count rate, isotope notation, radiation type, or nuclear-equation changes.
Common mistake
Common Mistake in Neutron Calculation
Students often forget to subtract the atomic number from the mass number when calculating the number of neutrons.
Remind students to use the formula: Number of Neutrons = Mass Number - Atomic Number, and to clearly identify each value before performing the subtraction.
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