June 2023 NY Regents Chemistry Exam
33 A potassium atom has a mass number of 37. What is the number of neutrons in this atom? (1) 15
(2) 18
(3) 22
(4) 37
Solution: Mass number = number of neutrons + number of protons. Number of protons is equal to the atomic number. We can find the atomic number of potassium on the Periodic Table. It is 19. Therefore, we have 37 = 19+x
x= 18
Answer: 2
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