The composition of a nuclide (atomic nucleus) is defined by the number of protons Z and the number of neutrons N, which sum to mass number A.Proton number Z, also named the atomic number, determines the position of an element in the periodic table.The approximately 3300 known nuclides are commonly represented in a chart with Z and N for its axes and the half-life for radioactive decay
Francium (Fr) has the lowest ionization energy, with a value of 4.0727eV. This ionization energy increases as one advances in a period, being greater in the group of nonmetals.
