Which isotope of barium has 82 neutrons?

• A. Ba-134
• B. Ba-138
• C. Ba-136
• D. Ba-137

Answer: (B)

Verified step by step guidance

1. Recall that the number of neutrons in an isotope is given by the difference between the mass number (A) and the atomic number (Z): \(\text{Number of neutrons} = A - Z\).
2. Identify the atomic number (Z) of barium (Ba), which is 56. This means every barium atom has 56 protons.
3. For each isotope option, subtract 56 from the mass number to find the number of neutrons. For example, for Ba-134, calculate \$134 - 56$.
4. Compare the calculated number of neutrons for each isotope to 82 to find which isotope has exactly 82 neutrons.
5. Select the isotope whose neutron count matches 82 as the correct answer.