The number of neutrons in is

Answer and explanation

Correct answer: A. 12

  1. Step 1: In standard isotope notation , denotes the mass number (total nucleons) and denotes the atomic number (total nuclear protons).
  2. Step 2: For the isotope , the mass number is and the atomic number is .
  3. Step 3: The number of neutrons in the nucleus is calculated by subtracting the atomic number from the mass number: .
Answer
12.
Why not the others: 34 is the sum of mass number and atomic number (); 23 is the total mass number (protons plus neutrons); 11 is the atomic number (number of protons).

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