Diamond crystal. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. The two most common allotropes of pure carbon are diamond and graphite. In graphite the bonds are sp orbital hybrids and the atoms form in planes with each bound to three nearest neighbors 120 degrees apart. In diamond they are sp and the atoms form tetrahedra with each bound to four nearest neighbors. Tetrahedra are rigid, the bonds are strong, and of all known substances diamond has the greatest number of atoms per unit volume, which is why it is both the hardest
Naming of chemical elements the 1970s (when the elements were discovered) to the 1990s, when the International Union of Pure and Applied Chemistry (IUPAC) created a tentative list of the element names for elements 104 to 109. The Americans, however, refused to agree with these names because seaborgium was not in the list. Thus, IUPAC reconsidered, and in 1996 named element 105 dubnium and element 106 seaborgium. When a pure element, comprising only one type of atom, nevertheless exists in multiple forms (allotropes) with different structure and properties, they are generally given different names; for example graphite and diamond are both forms of the