Chemical element of metals. Cu comes from Cuprum, Fe comes from Ferrum, Ag from Argentum. The symbols were not followed by a period (full stop) as with abbreviations. Later chemical elements were also assigned unique chemical symbols, based on the name of the element, but not necessarily in English. For example, sodium has the chemical symbol 'Na' after the Latin "natrium". The same applies to "W" (wolfram) for tungsten, "Fe" (ferrum) for iron, "Hg" (hydrargyrum) for mercury, "Sn" (stannum) for tin, "K" (kalium) for potassium, "Au" (aurum) for gold, "Ag" (argentum) for silver, "Pb" (plumbum) for lead, "Cu" (cuprum) for copper, and
Cobalt radiation therapy. Cobalt-57 (Co-57 or Co) is a cobalt radioisotope most often used in medical tests, as a radiolabel for vitamin B uptake, and for the Schilling test. Cobalt-57 is used as a source in Mössbauer spectroscopy and is one of several possible sources in X-ray fluorescence devices. Nuclear weapon designs could intentionally incorporate Co, some of which would be activated in a nuclear explosion to produce Co. The Co, dispersed as nuclear fallout, is sometimes called a cobalt bomb. Cobalt is essential to the metabolism of all animals. It is a key constituent of cobalamin, also known as vitamin