Question

Calculate the number of neutrons in the remaining atom after emission of an alpha particle from ${}_{92}^{238}U$ atom

• A. 146
• B. 145
• C. 144
• D. 143

Answer 1

Answer: (C)

144

Answer 2

On account of emission of an alpha particle, the atomic mass is decreased by 4 units and atomic number by 2 units

So, Atomic mass of daughter element = 234

Atomic number of daughter element = 90

Number of neutrons = Atomic mass – Atomic number

= 234 – 90 = 144