What is the number of electrons in an atom that has 3 protons and 4 neutrons

Atoms have an equal number of electron and protons, therefore the answer should be 3 :)

Since there is the same amount of agn03 in both silver chloride and silver nitrate they produce the same amount of moles. therefore silver chloride produces the same amount of silver nitrate, so your answer is 15.0 moles of silver nitrate. i hope this !