How many neutrons are in an isotope of uranium-235 if uranium has an atomic mass number of 92?
A) 143
B) 235
C) 92
D) 327

Question

Quizplus · Accepted Answer

The atomic mass number of uranium-235 is 235. Since the atomic mass number is the sum of protons and neutrons in an atom, we can subtract the atomic number (number of protons) from the atomic mass number to find the number of neutrons. 
92 (atomic number) + number of neutrons = 235 (atomic mass number)
Number of neutrons = 235 - 92
Number of neutrons = 143

How Many Neutrons Are in an Isotope of Uranium-235 If