THE STABILITY OF ISOTOPES
2 marks · Easy| Isotope | Number of protons | Number of neutrons |
|---|---|---|
| Carbon-12 | 6 | 6 |
| Carbon-13 | 6 | 7 |
| Carbon-14 | 6 | 8 |
Compare the stability of carbon-12 and carbon-14 and give a reason for your answer based on their neutron numbers.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Carbon-12 is more stable because it has an equal number of protons and neutrons, but carbon-14 has extra neutrons making it less stable.
Also accept: Carbon-12 is stable, but carbon-14 is unstable because of too many neutrons.
Common mistakes: Carbon-14 is more stable because it has more neutrons.
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Identifies carbon-12 as more stable (or carbon-14 as unstable)
B1 · 1 mark · Links reason to number of neutrons (carbon-14 has too many neutrons for stability)
Worked solution
Carbon-12 is the most stable isotope as it has 6 protons and 6 neutrons. Carbon-14 has 8 neutrons but only 6 protons, so it is less stable and radioactive.