Tentukan nomor atom dan massa unsur dari proton =55 neutron =78 Proton=45 nuetron 58

proton =55 neutron =78
nomer atom = proton = 55
nomer massa = p + n = 55 + 78 = 133

Proton=45 nuetron 58
nomer atom = p = 45
nomer massa = p + n = 45 + 58 = 103