What is the composition of the polonium atom?

The ordinal number of the element polonium in Mendeleev’s periodic table is 84. This indicates that the nucleus contains 84 protons. The mass of the isotope polonium with the longest half-life is 209 atomic units. From this it follows that in addition to protons, the nucleus also contains 209 – 84 = 125 neutrons. Since the atom is generally neutral, its electron shell should contain 84 electrons. It is known about the existence of 32 more isotopes of polonium with mass numbers from 188 to 220. They contain from 104 to 136 neutrons, while the number of protons and electrons remains the same – 84.
Answer: There are 84 protons and 125 neutrons in the nucleus, the electron shell is 84 electrons.