- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A chemical element, Au, atomic number 79 and atomic weight 196.967, a deep yellow, soft, and very dense metal. Gold is classed as a heavy metal and as a noble metal; commercially, it is the most familiar of the precious metals. Copper, silver, and gold are in the same group of the periodic table of elements. The Latin name for gold, <i>aurum</i> (glowing dawn), is the source of the chemical symbol Au. There is only one stable isotope of gold, that of mass number 197.
Industry:Science
A chemical element, B, atomic number 5, atomic weight 10.811, in group 13 of the periodic table. It has three valence electrons and is nonmetallic in behavior. It is classified as a metalloid and is the only nonmetallic element which has fewer than four electrons in its outer shell. The free element is prepared in crystalline or amorphous form. The crystalline form is an extremely hard, brittle solid. It is of jet-black to silvery-gray color with a metallic luster. One form of crystalline boron is bright red. The amorphous form is less dense than the crystalline and is a dark-brown to black powder. In the naturally occurring compounds, boron exists as a mixture of two stable isotopes with atomic weights of 10 and 11.
Industry:Science
A chemical element, Ba, with atomic number 56 and atomic weight of 137.34. Barium is eighteenth in abundance in the Earth's crust, where it is found to the extent of 0.04%, making it intermediate in amount between calcium and strontium, the other alkaline-earth metals. Barium compounds are obtained from the mining and conversion of two barium minerals. Barite, barium sulfate, is the principal ore and contains 65.79% barium oxide. Witherite, sometimes called heavy spar, is barium carbonate and is 72% barium oxide.
Industry:Science
A chemical element, Be, atomic number 4, with an atomic weight of 9.0122. Beryllium, a rare metal, is one of the lightest structural metals, having a density about one-third that of aluminum. Some of the important physical and chemical properties of beryllium are given in the <b>table</b>. Beryllium has a number of unusual and even unique properties.
Industry:Science
A chemical element, Br, atomic number 35, atomic weight 79.909, which normally exists as Br<sub>2</sub>, a dark-red, low-boiling but high-density liquid of intensely irritating odor. This is the only nonmetallic element that is liquid at normal temperature and pressure. Bromine is very reactive chemically; one of the halogen group of elements, it has properties intermediate between those of chlorine and iodine.
Industry:Science
A chemical element, C, with an atomic number of 6 and an atomic weight of 12.01115. Carbon is unique in chemistry because it forms a vast number of compounds, larger than the sum total of all other elements combined. By far the largest group of these compounds are those composed of carbon and hydrogen. It has been estimated that there are at least 1,000,000 known organic compounds, and this number is increasing rapidly each year. Although the classification is not rigorous, carbon forms another series of compounds, classified as inorganic, comprising a much smaller number than the organic compounds.
Industry:Science
A chemical element, Ca, of atomic number 20, fifth among elements and third among metals in abundance in the Earth's crust, Calcium compounds make up 3.64% of the Earth's crust. The physical properties of calcium metal are given in the table. The metal is trimorphous and is harder than sodium, but softer than aluminum. Like beryllium and aluminum, but unlike the alkali metals, it will not cause burns on the skin. It is less reactive chemically than the alkali metals and the other alkaline-earth metals.
Industry:Science
A chemical element, Ce, atomic number 58, atomic weight 140.12. It is the most abundant metallic element of the rare-earth group in the periodic table. The naturally occurring element is made up of the isotopes <sup>136</sup>Ce, <sup>138</sup>Ce, <sup>140</sup>Ce, and <sup>142</sup>Ce. A radioactive α-emitter, <sup>142</sup>Ce has a half-life of 5 × 10<sup>15</sup> years. Cerium occurs mixed with other rare earths in many minerals, particularly monazite and blastnasite, and is found among the products of the fission of uranium, thorium, and plutonium. See also: Periodic table
Industry:Science
A chemical element, Cf, atomic number 98, the ninth member of the actinide series of elements. Its discovery and production have been based upon artificial nuclear transmutation of radioactive isotopes of lighter elements. All isotopes of californium are radioactive, with half-lives ranging from a minute to about 1000 years. Because of its nuclear instability, californium does not exist in the Earth's crust.
Industry:Science
A chemical element, Cl, atomic number 17 and atomic weight 35.453. Chlorine exists as a greenish-yellow gas at ordinary temperatures and pressures. It is second in reactivity only to fluorine among the halogen elements, and hence is never found free in nature, except at the elevated temperatures of volcanic gases. It is estimated that 0.045% of the Earth's crust is chlorine. It combines with metals, nonmetals, and organic materials to form hundreds of chlorine compounds, the most important of which are discussed here.
Industry:Science
