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The nucleus of an atom of K-42 contains (1) 19 protons and 23 neutrons (2) 19 protons and 42 neutrons (3) 20 protons and 19 neutrons (4) 23 protons and 19 neutrons

Ramon Kelly

in Chemistry

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Kaitlin Dean on June 16, 2018

The atomic number is the number of protons, while atomic mass is the number of protons plus number of neutrons. By definition, the potassium (K) has the atomic number 19, so it must have 19 protons. If you have a mass of 42, then the number of neutrons is 42-19 = 23 neutrons. This is the option (1).


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