What is the mass number of an iron atom that has 28 neutrons?

• A. 54
• B. 56
• C. 26
• D. 28

Answer: (A)

Verified step by step guidance

1. Recall that the mass number (A) of an atom is the sum of the number of protons (Z) and neutrons (N) in its nucleus. This can be expressed as: \(A = Z + N\).
2. Identify the atomic number (Z) of iron (Fe) from the periodic table. The atomic number represents the number of protons in the atom.
3. Use the given number of neutrons (N = 28) and the atomic number of iron to calculate the mass number using the formula: \(A = Z + 28\).
4. Substitute the atomic number of iron into the equation to find the mass number.
5. Interpret the result as the mass number of the iron atom with 28 neutrons.