THE STABILITY OF ISOTOPES
2 marks · EasyHow does the number of neutrons affect whether an isotope is stable or unstable?
What can happen if an atom has too few neutrons?
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(a) The right number of neutrons makes an isotope stable; too many or too few neutrons make it unstable.
(b) If an atom has too few neutrons, it may become unstable and can decay.
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Marking points
B1 (a) · 1 mark · Explains that the number of neutrons must be in the right range for stability; otherwise, the isotope is unstable.
B1 (b) · 1 mark · States that too few neutrons make an atom unstable (it will decay).
Worked solution
a) The number of neutrons helps determine if the nucleus is stable—too many or too few neutrons make it unstable.
b) If there are too few neutrons, the nucleus will not stay together and become unstable, leading to decay.