Thulium Sulfide

See more Thulium products. Thulium (atomic symbol: Tm, atomic number: 69) is a Block F, Group 3, Period 6 element with an atomic weight of 168.93421. The number of electrons in each of Thulium's shells is [2, 8, 18, 31, 8, 2] and its electron configuration is [Xe]4f¹³6s². The thulium atom has a radius of 176 pm and a Van der Waals radius of 227 pm. In its elemental form, thulium has a silvery-gray appearance. Thulium is representative of the other lanthanides (rare earths) and similar in chemistry to yttrium. It is the least abundant of the rare earth elements. Thulium emits blue upon excitation, and is used in flat panel screens that depend critically on bright blue emitters. Thulium was discovered and first isolated by Per Teodor Cleve in 1879. It is named after "Thule," which is the ancient name of Scandinavia.

See more Sulfur products. Sulfur (or Sulphur) (atomic symbol: S, atomic number: 16) is a Block P, Group 16, Period 3 element with an atomic radius of 32.066. The number of electrons in each of Sulfur's shells is 2, 8, 6 and its electron configuration is [Ne] 3s² 3p⁴. In its elemental form, sulfur has a light yellow appearance. The sulfur atom has a covalent radius of 105 pm and a Van der Waals radius of 180 pm. In nature, sulfur can be found in hot springs, meteorites, volcanoes, and as galena, gypsum, and epsom salts. Sulfur has been known since ancient times but was not accepted as an element until 1777, when Antoine Lavoisier helped to convince the scientific community that it was an element and not a compound.