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Beta decay producing barium-137 comes from which parent nucleus? Barium has atomic number 56.
ACesium-137
BXenon-137
CLanthanum-137
DIodine-137
Answer & Solution
Correct answer: A. Cesium-137
1. Beta-minus decay increases the atomic number of the parent nucleus by one, while the mass number stays the same.
2. Since barium-137 has atomic number 56 as the product, the parent must have atomic number 55.
3. The element with atomic number 55 is cesium, giving cesium-137 as the parent.
4. Xenon (54), lanthanum (57), and iodine (53) do not have atomic number 55.
5. So cesium-137 is correct.
_Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.2 Nuclear Forces and Radioactivity_
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