selenium

Se Selenium 78.971 **Discovery Date:** 1817 **Discovered By:** Jöns Jacob Berzelius ** Origin Of The Name: ** The name is derived from 'selene', the Greek name for the Moon  ** Allotropes: ** Red Se, Grey Se, Black Se   **Group:**16 **Melting point:**220.8°C, 429.4°F, 494 K **Period:**4 **Boiling point:**685°C, 1265°F, 958 **Block:**p **Density (g cm−3):**4.809 **Atomic number:**34 **Relative atomic mass:**78.971 **State at 20°C:**Solid **Key isotopes:**80Se **Electron configuration:**[Ar] 3d104s24p4 **CAS number:**7782-49-2 **ChemSpider ID:** 4885617 ChemSpider is a free chemical structure database  

3 by: Miles Griffith