A nucleus weighs less than its sum of nucleons, a quantity known as the:
Correct answer: A. Mass defect
- A. Mass defect
- B. Binding energy
- C. Packing fraction
- D. None of these
Explanation
The mass of a nucleus is less than the sum of its nucleons because a small amount of its mass is transformed into energy when the nucleus is formed. When nucleons come together to form a nucleus, they experience a strong repulsive force which is the strong nuclear force. To overcome this repulsion, the nucleons have to do work, and this work requires energy which is taken from their mass. This is called mass defect. It is given by: ∆m = Zmproton + (A - Z )mneutron - mnucleus A = Mass number , Z= Atomic number
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Atomic nuclei contain protons and neutrons, with nuclear size, mass defect and binding energy describing their stability. The work covers alpha, beta and gamma decay, decay equations, half-life and decay rate, along with radiation safety and medical applications such as imaging, radiotherapy and tracers.
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