Question

sodium atom has an atomic mass of 23 U and 11 protons in its nucleus how many neutrons does it have​

Answer 1

It is said that atomic mass is the sum of number of neutrons and protons present in the nucleus.

Atomic mass = No. of protons + No. of neutrons.

Given atomic mass = 23

no. of protons = 11

Therefore no. of neutrons = 12

Answer 2

no of neutrons= mass number- no.of protons

                       = 23-11

                       =12

hence it has 12 neutrons