Which isotope is represented by an atom with 2 protons and 4 neutrons?

• A. beryllium-6
• B. helium-6
• C. lithium-6
• D. helium-4

Answer: (B)

Verified step by step guidance

1. Identify the number of protons in the atom, which determines the element. Here, the atom has 2 protons, so the element is helium (since helium has atomic number 2).
2. Determine the number of neutrons given, which is 4 in this case.
3. Calculate the mass number (A) of the isotope by adding the number of protons (Z) and neutrons (N): \(A = Z + N = 2 + 4\).
4. Combine the element name with the mass number to name the isotope. Since the element is helium and the mass number is 6, the isotope is helium-6.
5. Verify that the isotope name matches the options given and select helium-6 as the correct answer.