If an atom has 17 electrons and its mass number is 35, calculate the following: - number of protons - number of neutrons -atomic number

Electrons, Protons and the Atomic Number is the exact same. So 
Protons - 17
Atomic Number -  17

and the neutrons come by subtracting the protons from the Atomic Mass, which in this case 35. 
35-17 = 18
Neutrons = 18

Protons = 17
Atomic Number = 17
Neutrons = 18