Measurement of lawrencium’s ionization energy raises questions

Nature : The first ionization energy for an element is the energy needed to remove an electron from an atom’s outermost orbital shell. Despite being among the defining characteristics of elemental chemistry, ionization energies have been accurately determined only up to element 99, einsteinium. Now, Tetsuya Sato of the Japan Atomic Energy Agency (JAEA) in Tokai and his colleagues have measured the ionization energy of lawrencium-256, element 103. The task was difficult because the isotope has a half-life of about 27 s. The measured energy was just 4.96 eV, the fifth lowest of any known element. That value suggests that lawrencium is chemically most like the elements in the first column of the periodic table such as sodium and potassium, which each have a single, very loosely bound outer electron. Like those elements, it seems that its outer electron is in a p shell . However, lawrencium is usually depicted as the last element in the separated row of elements that are subordinate to the column under scandium and yttrium. Those elements’ external orbital is either a d or an f. The measurement of lawrencium’s ionization energy could lead to a reorganization of the periodic table.