![]() The following year he extracted impure chromium from reducing chromium (III) oxide with charcoal in 1798.Ĭhromium originates from the Ancient Greek word, χρώμα (chroma), which means color. Louis-Nicolas Vauquelin (1763–1829) 2, a French chemist, produced chromium (III) oxide from crocoite in 1797. Along with many other oxides, it is used as a compound when polishing (also called stropping) the edges of knives, razors, surfaces of optical devices etc. In 1761, Johann Gottlob Lehmann (1719–1767) 2, a German geologist, discovered the mineral crocoite in the Urals, which is now known to be lead chromate. Chromium (III) oxide is a precursor to the magnetic pigment chromium dioxide, by the following reaction: 7 Cr. chromium-51 is a radioisotope used as a tracer in nuclear medicine for labeling red cells.It is a known carcinogen and also a serious dermatological irritant.Ĭhromium-containing fumes have also been implicated as a precipitant in metal fume fever, although this is contentious 3. The toxicity of hexavalent chromium (Cr 6+) is widely recognized leading to global bans and restrictions on its use. It is the only mineral for which the US and European Union do not concur on its essential status. Its importance in normal human physiology is contentious, indeed the European Union no longer classifies it as an essential trace element, whilst the USA, Japan and Australia still do. Nevertheless it is often included in over the counter dietary supplements in its trivalent form and it is not thought to be toxic at these low (microgram) doses. Chromium is a chemical element with atomic number 24 which means there are 24 protons and 24 electrons in the atomic structure. Since its true biological function remains in the balance, it is difficult to assign a recommended allowance. In total an additional 19 unstable isotopes are known, ranging from the stablest, 50Cr with a half life of 1.8 × 10 17 years, and 51Cr with a half-life of 27.7 days, and the rest with half lives all shorter than a day. 52Cr is the commonest on Earth, accounting for 83.8% of the total. In nature, chromium exists as three stable isotopes: 52Cr, 53Cr and 54Cr. In human toxicology hexavalent chromium ( Cr 6+) is key. It exists in multiple oxidation states, but physiologically the trivalent ( Cr 3+) state is the most important. 1) symbol cr atomic number 24 Chromium is element number 24, so a neutral atom would have 24 protons and 24 electr View the full answer. Like iron, it is one of the transition metals. Chromium has the atomic number 24 with an atomic weight of 51.9961 g/mol.
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