Silicon (Si). Diagram of the nuclear composition and electron configuration of an atom of silicon-28 (atomic number: 14), the most common isotope of this element. The nucleus consists of 14 protons (red) and 14 neutrons (yellow). 14 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. Silicon, a solid metalloid, is in group 14, period 3, and the p-block of the periodic table. It is one of the elements used in semiconductors, forming the basis of computer technology. It has a melting point of 1414 degrees Celsius.