An atom with Z = 31 and A = 69 contains ________ protons and ________ neutrons.
A)31;69
B)69;31
C)31;38
D)38;31
E)31;100

Question

Quizplus · Accepted Answer

Z represents the atomic number which is the number of protons in the nucleus. Therefore, this atom contains 31 protons. A represents the mass number which is the total number of protons and neutrons in the nucleus. Subtracting the number of protons from the mass number gives the number of neutrons, which is 38. Therefore, the correct answer is C) 31 protons and 38 neutrons.

An Atom with Z = 31 and a = 69