Neodymium is a Block F, Group 3, Period 6 element. The electronic configuration is [Xe]4f⁴6s². In its elemental form neodymium's CAS number is 7440-00-8. The neodymium atom has a radius of 181.4.pm and it's Van der Waals radius is 181.pm. Neodymium is the most abundant of the rare earths after cerium and lanthanum. Neodymium is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity); metals in the form of foil, sputtering target, and rod, and compounds as submicron and nanopowder. Primary applications include lasers, glass coloring and tinting, dielectrics and, most importantly, as the fundamental basis for neodymium-iron-boron permanent magnets. Neodymium has a strong absorption band centered at 580 nm, which is very close to the human eye's maximum level of sensitivity making it useful in protective lenses for welding goggles.