How many protons are present in an atom of aluminum-28?

• A. 14
• B. 13
• C. 15
• D. 28

Answer: (B)

Verified step by step guidance

1. Identify the element given, which is aluminum. The atomic number of aluminum determines the number of protons in the atom.
2. Recall that the atomic number (Z) of an element is equal to the number of protons in its nucleus. For aluminum, the atomic number is 13.
3. Understand that the number following the element name (in this case, 28 in aluminum-28) represents the mass number (A), which is the sum of protons and neutrons.
4. Since the question asks for the number of protons, focus only on the atomic number, not the mass number.
5. Conclude that the number of protons in an atom of aluminum-28 is equal to the atomic number of aluminum, which is 13.