Period 6 element living organism. Tungsten interferes with molybdenum and copper metabolism, and is somewhat toxic to animal life. Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metal in group 7 of the periodic table. With an "estimated" average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. The free element has the third-highest melting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper ore's extraction and refinement. Rhenium
Melting whose viscosity increases to a point due to polymerization and then decreases with higher temperatures in its molten state. Some organic compounds melt through mesophases, states of partial order between solid and liquid. From a thermodynamics point of view, at the melting point the change in Gibbs free energy "∆G" of the substances is zero, but there are non-zero changes in the enthalpy ("H") and the entropy ("S"), known respectively as the enthalpy of fusion (or latent heat of fusion) and the entropy of fusion. Melting is therefore classified as a first-order phase transition. Melting occurs when the Gibbs free