Beryllium has several isotopes. How many neutrons are present in the most abundant isotope of beryllium, Be-9?

• A. 5
• B. 9
• C. 4
• D. 2

Answer: (C)

Verified step by step guidance

1. Identify the atomic number of beryllium (Be), which is the number of protons in the nucleus. For beryllium, the atomic number is 4.
2. Recognize that the isotope notation Be-9 means the isotope has a mass number of 9. The mass number is the total number of protons and neutrons in the nucleus.
3. Use the relationship between mass number (A), number of protons (Z), and number of neutrons (N): \(A = Z + N\).
4. Rearrange the formula to solve for the number of neutrons: \(N = A - Z\).
5. Substitute the known values: \(N = 9 - 4\), which gives the number of neutrons in the most abundant isotope of beryllium.