What is the mass number of an atom of potassium that has 20 neutrons?
A)15
B)19
C)35
D)39
E)59

Name: What is the mass number of an atom of potassium that has 20 neutrons? A)15 B)19 C)35 D)39 E)59
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Question

Quizplus · Accepted Answer

The mass number of an atom is the sum of its protons and neutrons. Potassium has an atomic number of 19 (meaning it has 19 protons), so an atom of potassium that has 20 neutrons would have a mass number of 19 + 20 = 39. Therefore, the correct answer is choice D.

What Is the Mass Number of an Atom of Potassium