Tellurium (Te). Diagram of the nuclear composition and electron configuration of an atom of tellurium-128 (atomic number: 52), an isotope of this element. The nucleus consists of 52 protons (red) and 76 neutrons (yellow). 52 electrons (white) bind to the nucleus, successively occupying available electron shells (rings). The stability of an element's outer electrons determines its chemical and physical properties. Tellurium is a metalloid in group 16, period 5, and the p-block of the periodic table. It has a melting point of 450 degrees Celsius. A rare element, it is used mostly in alloys, solar panels, and semiconductors.