Lawrencium (Lr). Diagram of the nuclear composition, electron configuration, chemical data, and valence (outer electron) orbitals of an atom of lawrencium-262 (atomic number: 103), an isotope of this element. The nucleus consists of 103 protons (red) and 159 neutrons (orange). 103 electrons (white) successively occupy available electron shells (rings). Lawrencium, named after Ernest Lawrence and first synthesised in 1961, is an actinide and transuranic element in group 3, period 7, and the d-block of the periodic table. Actinides are soft radioactive metals. Lawrencium-262 is the most stable isotope of lawrencium, with a half-life of 216 minutes.