Neodymium is a Block F, Group 3, Period 6 element. The number of electrons in each of Neodymium's shells is 2, 8, 18, 22, 8, 2 and its electronic configuration is [Xe] 4f⁴ 6s². 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. It is also used in CRT displays to enhance contrast between reds and greens and highly valued in glass manufacturing for its attractive purple coloring. Neodymium is included in many formulations of barium titanate, used as dielectric coatings and in multi-layer capacitors essential to electronic equipment. Neodymium was first discovered by Carl Aer von Welsbach in 1885. The name originates from the Greek words 'neos didymos', meaning new twin. See Neodymium research below.