Question

How many protons, electrons, and neutrons does an atom with atomic number 50 and mass number 125 contain?

Answer 1

The number of protons in an atom is equal the atomic number (= 50)

The sum of the Neutrons and Protons is the Atomic Mass (=125)
Neutrons + Protons=125

Plug in for the protons (50)
Neutrons +(50)=125

Then, once solved, we have Neutrons = 75

Assuming the atom is NOT an ion, the amount of electrons is equal to the number of protons. (protons=electrons=50=50)

Therefore:
There are 50 electrons, 50 protons, and 75 electrons.