The number of neutrons present in an element having mass number 226 and atomic number 88 is :

Answer: Option B

The mass number is a count of the number of particles in an atom's nucleus which is made up of protons and neutrons. In other words,
Mass Number = Number of Protons + Number of Neutrons.
The atomic number is the number of protons in an atom of an element, i.e., 226 = 88 + number of Neutrons. So, the number of neutrons= 226 – 88= 138.