What is the mass number of the most abundant isotope of the element copper (Cu)?

• A. 65
• B. 63
• C. 29
• D. 47

Answer: (B)

Verified step by step guidance

1. Understand that the mass number of an isotope is the total number of protons and neutrons in its nucleus.
2. Recall that the atomic number of copper (Cu) is 29, which means every copper atom has 29 protons.
3. Identify the most abundant isotope of copper by referring to its natural isotopic distribution; the most common isotope has a mass number close to the average atomic mass of copper.
4. Since the most abundant isotope has a mass number of 63, calculate the number of neutrons by subtracting the atomic number from the mass number: \(\text{neutrons} = 63 - 29\).
5. Conclude that the mass number of the most abundant isotope of copper is 63, representing the sum of 29 protons and the corresponding number of neutrons.