Which of the following isotopes has 45 neutrons?

• A. Titanium-45 (Ti, atomic number 22)
• B. Scandium-66 (Sc, atomic number 21)
• C. Vanadium-68 (V, atomic number 23)
• D. Calcium-45 (Ca, atomic number 20)

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 mass number (the number after the element name) and the atomic number (given for each element) for each isotope option.
3. Calculate the number of neutrons for Titanium-45: \$45 - 22$.
4. Calculate the number of neutrons for Scandium-66: \$66 - 21$.
5. Calculate the number of neutrons for Vanadium-68: \$68 - 23\(, and for Calcium-45: \)45 - 20$, then compare all results to find which isotope has exactly 45 neutrons.