Chromium atomic weight

The interchange reaction implies the removal of one atom of /I at the surface for each atom of B deposited. It therefore takes place with a minimum change in weight or dimensions of the article (A). U A and B have similar atomic weights, as in the case of iron and chromium, interchange reaction will produce little change in weight and no measurable increase in dimension, whatever the thickness of the diffusion layer. 

Chromium in the crystalline form is a steel-gray, lustrous, hard metal characterized by an atomic weight of 51.996, an atomic number of 24, a density of 7.14 g/cm3, a melting point of 1857°C, and a boiling point of 2672 C. Four chromium isotopes occur naturally Cr-50 (4.3%), -52 (83.8%), -53 (9.6%), and -54 (2.4%), and seven are man-made. Elemental chromium is very stable but is not usually found pure in nature. Chromium can exist in oxidation states ranging from -2 to +6, but is most frequently found in the environment in the trivalent (+3) and hexavalent (+6) oxidation states. The +3 and +6 forms are the most important because the +2, +4, and +5 forms are unstable and are rapidly converted to +3, which in turn is oxidized to +6 (Towill et al. 1978 Langard and Norseth 1979 Ecological Analysts 1981 USPHS 1993). 

Sheilds WR, Murphy TJ, Catanzaro EJ, Garner J (1966) Absolute isotopic abundance ratios and the atomic weight of a reference sample of chromium. J Res Natl Bur Standards 70A(2) 193-197 Shukolyukov A, Lugmair GW (1998) Isotopic evidence for the Cretaceous-Tertiary impactor and its type. Science 282(5390) 927-929... 

Look up the atomic weight of chromium and find the atomic ratio in each oxide. Write the simplest formula of each oxide. 

Moissan 3 in 1880 called attention to the fact that the affinities of chromium, manganese, iron, cobalt, and nickel for oxygen and the heats of formation of oxides, chlorides, bromides, iodides, and sulphides decrease as the atomic weights rise. 

Important new insights into the various ways in which the elements could be interrelated were gained during the middle decades of the nineteenth century. The German chemist Leopold Gmelin (1788-1853) pointed out in 1843 that whereas in some triads the atomic weights hardly differed at all, for example, in chromium-manganese-iron, in other triads... 

If 100 gm. of lead nitrate produce 97.576 gm. of lead chromate, what is the atomic weight of chromium (Equation is K2Cr04 + Pb(N03)2 = PbCr04 + 2 KNO3.)... 

Atomic Weight.—From a consideration of the vapour densities of volatile compounds of chromium, and from the application of Dulong and Petit s Law, it is obvious that the atomic weight of chromium is about 52—that is, three times the chemical equivalent of chromium in chromic salts, or six times its combining weight in derivatives of chromium trioxide. Chromium thus exhibits di-, tri-, and hexa-valency in the chromous salts, chromic salts, and chromates and diehromates respectively. 

For a review of the work done on the Atomic Weight of chromium ace Clarko, A EecalculcUion ofiJie Atomic Weights, Smithsonian Misc. GoU., 1910, 54, No. 3, p. 340. Also Baxter, Mueller, and Hines, Ohem. News, 1909, 100, 181. 

Atomic Weight.—For reasons similar to those applying in the case of chromium (p. 16), the atomic %veight of molybdenum is three times the equivalent of the metal in the molybdic salts, or six times that in the molybdates. Molybdenum may be di-, tri-, or hexa-valent. 

Atomic Weight.— Like chromium and molybdenum, tungsten may in its compounds be di-, tri-, or hexa-valent from a consideration of its specific heat, the isomorphism of its compounds, its position in the... 

In 1872 Mendeleeft pointed out that there was no place in the Periodic Table for a trivalent element of atomic weight 120, and drew attention to the similarity of uranium to chromium, molybdenum, and tungsten he therefore suggested that the atomic weight should be doubled, so that uranium could be placed below these elements in the table. He also formulated the oxides, by analog with those of the other elements in the group, as follows uranous oxide UOg, urano-... 

Chromium has an atomic number of 24, an atomic weight of 51.996 consisting of four stable isotopes ( Cr = 84%), and a density of 7.14 gcm (Adriano, 1986). Crystalline Cr is steel-gray in color, lustrous, hard metal that has a melting point of 1,900 °C and a boiling point of 2,642 °C. It belongs to group VIb of the transition metals and in aqueous solution Cr exists primarily in the trivalent (4-3) and hexavalent (+6) oxidation states. Chromium, as well as Zn, are the most abundant of the heavy metals with a concentration of about 69p,gg in the hthosphere (Li, 2000). 

Step 3 We then use the atomic weight of Cr to convert the number of moles of chromium atoms to mass of chromium. 

Atomic weight m27 B, Moleouhr weight unknown. Specific gravity 2 0. Fms at about 460 . Atomicity 4 < it almye a peevdo-triai. Evidence of atomicity .—Analogy with iron and chromium. 

It would appear that the adsorption strength of CO falls off with decreasing atomic weight for this series of elements, particularly when going from molybdenum to chromium. There is, however, a significant difference in the atomic diameter of these two elements in their normal body-centered cubic structures (Mo = 2.72 A Cr = 2.5 A). 

How would you prepare a sample of really dry chromium trioxide, of purity good enough for an atomic-weight determination ... 

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