Period 2 element a supplement for the prevention and treatment of osteoporosis and arthritis. Carbon is the chemical element with atomic number 6, occurring as C, C and C. At standard temperature and pressure, carbon is a solid, occurring in many different allotropes, the most common of which are graphite, diamond, the fullerenes and amorphous carbon. Graphite is a soft, hexagonal crystalline, opaque black semimetal with very good conductive and thermodynamically stable properties. Diamond however is a highly transparent colourless cubic crystal with poor conductive properties, is the hardest known naturally occurring mineral and has the highest refractive index of all gemstones. In
Pure subgroup Pure subgroup In mathematics, especially in the area of algebra studying the theory of abelian groups, a pure subgroup is a generalization of direct summand. It has found many uses in abelian group theory and related areas. A subgroup formula_1 of a (typically abelian) group formula_2 is said to be pure if whenever an element of formula_1 has an formula_4 root in formula_2, it necessarily has an formula_4 root in formula_1. Formally, formula_8 is solvable in formula_2 formula_10 is solvable in formula_1. Pure subgroups are also called isolated subgroups or serving subgroups and were first investigated in Prüfer's 1923 paper