Chromium s

The key to hexavalent chromium s mutagenicity and possible carcinogenicity is the abiHty of this oxidation state to penetrate the cell membrane. The Cr(VI) Species promotes DNA strand breaks and initiates DNA—DNA and DNA-protein cross-links both in cell cultures and in vivo (105,112,128—130). The mechanism of this genotoxic interaction may be the intercellular reduction of Cr(VI) in close proximity to the nuclear membrane. When in vitro reductions of hexavalent chromium are performed by glutathione, the formation of Cr(V) and glutathione thiyl radicals are observed, and these are beHeved to be responsible for the formation of the DNA cross-links (112). 

Cr03 As a transition metal, chromium forms more than one stable cation. Name the metal first, using a Roman numeral to designate chromium s charge. Each of the three oxide anions has a -2 charge. To maintain net charge neutrality, Cr must be +6, so the name of the compound is chromium(VI) oxide. 

H thorium K zirconium L lithium M manganese N nickel P lead Q silver R chromium S silicon T tin W yttrium Y antimony Z zinc Second part... 

To solve chromium s line, notice that chromium has a mass number of 52 and an atomic number of 24. This tells you that the number of protons is 24, because the atomic number and the number of protons are the same. To determine the number of neutrons, you simply subtract the atomic number from the mass number 52-24=28 neutrons. Finally, the number of protons is equal to the number of electrons. Continue this process to fill in the info for iridium and molybdenum. 

These experts collectively have knowledge of chromium s physical and chemical properties, toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer review specified in Section 104(I)( 13) of the Comprehensive Environmental Response, Compensation, and Liability Act, as amended. 

The correct answer is (B). Although choices (B) and (D) each have 24 electrons, (B) is the better answer because of chromium s exceptional electron configuration. The chromium atom gains increased stability by promoting one of the 4s electrons to the vacant 3d orbital. This promotion creates half-filled orbitals, which increase stability. 

V. A. Korshunov, and M. S. Petrushevskii Several Singularities of the Structure of Liquid Alloys of Silicon with Iron, Manganese and Chromium. S. 171 in (476). 

Data for chromium s four naturally occurring isotopes is provided in the table below. Calculate chromium s atomic mass. 

During the period of discovery, chemists were surprised at chromium s different colors. When Lehmann dissolved the red lead chromate mineral from Yekaterinburg he observed and reported the green color of its hydrochloric acid soluHon. We say today that it is the trivalent chromium ion that is green. When VauqueHn boiled the powdered mineral with potassium carbonate and filtered he saw the yellow color of the filtrate. He had hexavalent chromium in his beaker. 

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