An atom has an atomic number of 19 and a mass number of 39. How many electron ,protons and neutrons does it have?
Which of the following statement is correct about the atom of an element ?
(a) an atom can have only protons and neutrons but no electrons.
(b) an atom can have only electrons and neutrons but no protons
(c) an atom can have only electron and proton but no neutron
(d) an atom must always have a proton, neutron and electron