Next is the helium atom which has two planetary electrons and whose nucleus contains two protons and two uncharged neutrons which tend to bind the two protons together (fig.1-2 [b]) similarly in fig1-2 (c) and (d) are shown atoms of lithium and beryllium under each figure is given the symbol used in nuclear physics the subscript is the atomic number and the upper number represents the atomic mass number oxygen atom (r016) has 8 orbital electrons and it's nucleus contains 8 protons and 8 neutrons heaviest atom is that of an element which is called kurchatovium by Russians and rutherfordium (106rd160)by Americans it was 104 electrons 104 protons and 156 neutron