Chemical element same atomic number, or number of protons. Nuclear scientists, however, define a pure element as one that consists of only one stable isotope. For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each. However it is not isotopically pure since ordinary copper consists of two stable isotopes, 69% Cu and 31% Cu, with different numbers of neutrons. However, a pure gold ingot would be both chemically and isotopically pure, since ordinary gold consists only of one isotope, Au. Atoms of chemically pure elements may bond to each other chemically in
Period 6 element shows in its compounds a wide variety of oxidation states ranging from −1 to +7. Discovered in 1925, rhenium was the last stable element to be discovered. It was named after the river Rhine in Europe. Nickel-based superalloys of rhenium are used in the combustion chambers, turbine blades, and exhaust nozzles of jet engines, these alloys contain up to 6% rhenium, making jet engine construction the largest single use for the element, with the chemical industry's catalytic uses being next-most important. Because of the low availability relative to demand, rhenium is among the most expensive of metals, with an average