Redirected from Chromium/Temp
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Name, Symbol, Number | Chromium, Cr, 24 | ||||||||||||||||||||||||||||||||||||
Chemical series | Transition metals | ||||||||||||||||||||||||||||||||||||
Group, Period, Block | 6 , 4 , d | ||||||||||||||||||||||||||||||||||||
Density, Hardness | 7140 kg/m3, 8.5 | ||||||||||||||||||||||||||||||||||||
Appearance | silvery metallic | ||||||||||||||||||||||||||||||||||||
Atomic Properties | |||||||||||||||||||||||||||||||||||||
Atomic weight | 51.9961 amu | ||||||||||||||||||||||||||||||||||||
Atomic radius (calc.) | 140 (166) pm | ||||||||||||||||||||||||||||||||||||
Covalent radius | 127 pm | ||||||||||||||||||||||||||||||||||||
van der Waals radius | n/a pm | ||||||||||||||||||||||||||||||||||||
Electron configuration | [Ar]3d54s1 | ||||||||||||||||||||||||||||||||||||
e- 's per energy level | 2, 8, 13, 1 | ||||||||||||||||||||||||||||||||||||
Oxidation states (Oxide) | 6,3,2 (strong acid) | ||||||||||||||||||||||||||||||||||||
Crystal structure | Cubic, body centered | ||||||||||||||||||||||||||||||||||||
Physical Properties | |||||||||||||||||||||||||||||||||||||
State of matter | solid (__) | ||||||||||||||||||||||||||||||||||||
Melting point | 2130 K (3375 °F) | ||||||||||||||||||||||||||||||||||||
Boiling point | 2945 K (4842 °F) | ||||||||||||||||||||||||||||||||||||
Molar volume | 7.23 ×10-3 m3/mol | ||||||||||||||||||||||||||||||||||||
Heat of vaporization | 344.3 kJ/mol | ||||||||||||||||||||||||||||||||||||
Heat of fusion | 16.9 kJ/mol | ||||||||||||||||||||||||||||||||||||
Vapor pressure | 990 Pa at 2130 K | ||||||||||||||||||||||||||||||||||||
Velocity of sound | 5940 m/s at 293.15 K | ||||||||||||||||||||||||||||||||||||
Miscellaneous | |||||||||||||||||||||||||||||||||||||
Electronegativity | 1.66 (Pauling scale) | ||||||||||||||||||||||||||||||||||||
Specific heat capacity | 450 J/(kg*K) | ||||||||||||||||||||||||||||||||||||
Electrical conductivity | 7.74 106/m ohm | ||||||||||||||||||||||||||||||||||||
Thermal conductivity | 93.7 W/(m*K) | ||||||||||||||||||||||||||||||||||||
1st ionization potential | 652.9 kJ/mol | ||||||||||||||||||||||||||||||||||||
2nd ionization potential | 1590.6 kJ/mol | ||||||||||||||||||||||||||||||||||||
3rd ionization potential | 2987 kJ/mol | ||||||||||||||||||||||||||||||||||||
4th ionization potential | 4743 kJ/mol | ||||||||||||||||||||||||||||||||||||
5th ionization potential | 6702 kJ/mol | ||||||||||||||||||||||||||||||||||||
6th ionization potential | 8744.9 kJ/mol | ||||||||||||||||||||||||||||||||||||
Most Stable Isotopes | |||||||||||||||||||||||||||||||||||||
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SI units & STP are used except where noted. |
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The most common oxidation states of chromium are +2, +3, and +6, with +3 being the most stable. +4 and +5 are relatively rare. Chromium compounds of oxidation state 6 are powerful oxidants.
In 1770, Peter Simon Pallas visited the same site as Lehmann and found a red "lead" mineral that had very useful properties as a pigment in paints. The use of Siberian red lead as a paint pigment developed rapidly. A bright yellow made from crocoite became a very fashionable color.
In 1797, Nicolas-Louis Vauquelin received samples of crocoite ore. He was able to produce chromium oxide (CrO3) by mixing crocoite with hydrochloric acid. In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven. He was also able to detect traces of chromium in precious gems, such as ruby, or emerald.
During the 1800s chromium was primarily used as a component of paints but now the primary use (85%) is for metal alloys, with the remainder used in the chemical industry and refractory and foundry industries.
Though native chromium deposits are rare, some native chromium metal has been discovered. The Udachnaya Mine in Russia produces samples of the native metal. This mine is a kimberlite pipe rich in diamonds, and the reducing environment so provided helped produce both elemental chromium and diamond.
Potassium dichromate is a powerful oxidizing agent and is the preferred compound for cleaning laboratory glassware of any possible organics. Chrome green is the green oxide of chromium, Cr2O3, used in enamel painting, and glass staining. Chrome yellow is a brilliant yellow pigment, PbCrO4, used by painters.
Chromium-53 is the radiogenic decay product of 53Mn. Chromium isotopic contents are typically combined with manganese isotopic contents and have found application in isotope geology[?]. Mn-Cr isotope ratios reinforce the evidence from 26Al and 107Pd for the early history of the solar system. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate an initial 53Mn/55Mn ratio that suggests Mn-Cr isotope systematics must result from in-situ decay of 53Mn in differentiated planetary bodies. Hence 53Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.
The isotopes of chromium range in atomic weight from 43 amu (43-Cr) to 67 amu (67-Cr). The primary decay mode before the most abundant stable isotope, 52-Cr, is electron capture and the primary mode after is beta.
The 1958 the World Heath Organization recommended a maximum allowable concentration of 0.05 mg/liter in drinking water for chromium (VI), based on health concerns. This recommendation has been reviewed a number of times and this value has not been revised in the meantime.
wikipedia.org dumped 2003-03-17 with terodump