Lawrencium
. Lawrencium, symbol Lr, artificially created radioactive metallic element with an atomic number of 103. Lawrencium is one of the transuranium elements of the periodic table . Named in honor of the American physicist Ernest Lawrence , it was discovered in 1961 at the Lawrence Berkeley National Laboratory of the University of California by American chemist Albert Ghiorso and his colleagues. A mixture of californium isotopes was bombarded with boron ions to produce short-lived lawrencium isotopes. Isotopes with mass numbers from 255 to 260 have been prepared. The most stable isotope, with a half-life of about 3 minutes, has a mass number of 260. Only small amounts of lawrencium have been produced. See also Radioactivity .