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Why did scientists conclude that the radiation discovered by Becquerel originates in the nucleus rather than in the electrons of an atom?

AIt only appears when heated to very high temperatures
BIt stays the same across temperature, pressure, and state
CIt changes with which compound the element forms
DIt disappears completely at low pressure
Answer & Solution
Correct answer: B. It stays the same across temperature, pressure, and state
1. Chemical reactions and atomic spectra depend on an atom's electrons, which are sensitive to temperature, pressure, compound, and ionization state. 2. Radioactivity was found not to vary with any of those factors, whether uranium was an element or part of a compound. 3. This independence, together with the huge energy released per event, pointed to the nucleus rather than the electrons as the source. 4. Radiation is not switched on only by heating, and it does not disappear at low pressure. 5. So the independence from temperature, pressure, and chemical or ionization state is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.2 Nuclear Forces and Radioactivity_
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