Question

carbon - 12 and carbon - 13 are isotopes of carbon. which of the following statements is correct?
they both have seven protons in the nucleus.
they both have the same mass number.
they both have seven neutrons in the nucleus.
they both have the same atomic number.

Explanation:

• Protons: For carbon, atomic number \(Z = 6\). So, number of protons \(=6\) for both \(C - 12\) and \(C - 13\). First option (7 protons) is wrong.
• Mass number: Mass number \(A\) for \(C - 12\) is \(12\) and for \(C - 13\) is \(13\). Second option (same mass number) is wrong.
• Neutrons: Number of neutrons \(N=A - Z\). For \(C - 12\), \(N = 12-6=6\); for \(C - 13\), \(N=13 - 6 = 7\). Third option (7 neutrons for both) is wrong.
• Atomic number: Atomic number \(Z\) (number of protons) is same (\(Z = 6\)) for isotopes.

Answer:

They both have the same atomic number.