Multiple choice Number of neutrons in 92X238 is 144 148 242 146 Reveal answer Fill a bubble to check yourself D Correct answer Explanation For X-238 with atomic number 92, neutrons = mass number - atomic number = 238 - 92 = 146. This element is uranium (U-238). Option A (144) would give mass 236, B (148) gives 240, and C (242) is the mass number itself.