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Question
Which are isotopes? An atom that has an atomic number of 20 and a mass number of 42 is an isotope of an atom that hasA) an atomic number of 21 and a mass number of 42.
B) an atomic number of 20 and a mass number of 40.
C) 22 neutrons and 20 protons.
D) 22 protons and 20 neutrons.
Answer
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