Sodium has an atomic number of 38 and a mass number of 88 how many neutrons are in one atom of strontium 88 50 38 126

Neutrons and protons each weight approximately 1 unit, while electrons weigh almost nil.

The atomic number tells us the number of protons (and electrons) there are in each atom.  

Thus the mass number (88)  is the total of the number of neutrons (N) and protons (38).

Therefore the number of neutrons is N=(88-38)=50