Respuesta :
Answer:
11
Explanation:
The formula you would use is
Protons = mass - neutrons
mass = 19
neutrons = 8
Protons = 19 - 8
Protons = 11
Subtract 8 from 19 to get the number of protons
Protons + neutrons = mass of an atom
Protons + neutrons = mass of an atom