Question

How many neutrons are there in ${}_{92}^{238}\text{U}$?

• A. 148
• B. 146
• C. 144
• D. 92

Answer 1

The correct option is B 146

Mass number = Number of neutrons + Atomic number (number of protons)

Number of neutrons = Mass number - Atomic number

Mass number of U = 238
Atomic number of U = 92

Therefore, number of neutrons of U
= 238 - 92
= 146