Chemical element of an element to exist in one of many structural forms is known as 'allotropy'. The standard state, also known as the reference state, of an element is defined as its thermodynamically most stable state at a pressure of 1 bar and a given temperature (typically at 298.15 K). In thermochemistry, an element is defined to have an enthalpy of formation of zero in its standard state. For example, the reference state for carbon is graphite, because the structure of graphite is more stable than that of the other allotropes. Several kinds of descriptive categorizations can be applied broadly to
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