Answer is: there are eighty-eight (88) protons in an atom.
The atomic number
(Z) determines total number of protons and uniquely identifies a chemical element, also the atomic number is equal to the number of electrons.
The atomic number
(Z) for this atom (radium) is eighty-eight.
The mass number
(A) is total number of protons and neutrons in a nucleus, in this example A = 220.
