Selenium Selenium Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth's crust. Selenium (from Ancient Greek (selḗnē) "Moon") was discovered in 1817 by Jöns Jacob Berzelius, who noted the similarity of the new element to the previously discovered tellurium (named for the Earth). Selenium is found in , where it
Group 3 element upper neighbor of yttrium, which he called "eka-boron". Swedish chemist Lars Fredrik Nilson and his team discovered the missing element in the minerals euxenite and gadolinite and prepared 2 grams of scandium(III) oxide of high purity. He named it scandium, from the Latin "Scandia" meaning "Scandinavia". Chemical experiments on the element proved that Mendeleev's suggestions were correct; along with discovery and characterization of gallium and germanium this proved the correctness of the whole periodic table and periodic law. Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev. Metallic scandium was produced for