Carbon (C). Diagram showing the nuclear composition and electron configuration of an atom of carbon-12 (atomic number: 6), the most common isotope of the element carbon. The nucleus consists of 6 protons (red) and 6 neutrons (yellow). Six 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. Carbon, which forms the basis of life on Earth, is a non-metal in group 14, period 2, and the p-block of the periodic table. In elemental form, it is a solid that burns when heated with oxygen.