- 行业: Printing & publishing
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- 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, Pd, atomic number 46, and atomic weight 106.4. A transition metal, palladium occurs in combination with platinum (Pt) and is the second most abundant platinum-group metal, accounting for 38% of the reserves of these metals.
Industry:Science
A chemical element, Pm, atomic number 61. Promethium is the “missing” element of the lanthanide rare-earth series. The atomic weight of the most abundant separated radioisotope is 147.
Industry:Science
A chemical element, Po, atomic number 84. Marie Curie discovered the radioisotope <sup>210</sup>Po in pitchblende. This isotope is the penultimate member of the radium decay series. All polonium isotopes are radioactive, and all are shortlived except the three α-emitters, artificially produced <sup>208</sup>Po (2.9 years) and <sup>209</sup>Po (100 years), and natural <sup>210</sup>Po (138.4 days).
Industry:Science
A chemical element, Pr, atomic number 59, and atomic weight 140.91. Praseodymium is a metallic element of the rare-earth group. The stable isotope 140.907 makes up 100% of the naturally occurring element. The oxide is a black powder, the composition of which varies according to the method of preparation. If oxidized under a high pressure of oxygen it can approach the composition PrO<sub>2</sub>. The black oxide dissolves in acid with the liberation of oxygen to give green solutions or green salts which have found application in the ceramic industry for coloring glass and for glazes.
Industry:Science
A chemical element, Pt, atomic number 78, and atomic weight 195.09. Platinum is a soft, ductile, white noble metal. The platinum-group metals—platinum, palladium, iridium, rhodium, osmium, and ruthenium—are found widely distributed over the Earth. Their extreme dilution, however, precludes their recovery, except in special circumstances. For example, small amounts of the platinum metals, palladium in particular, are recovered during the electrolytic refining of copper.
Industry:Science
A chemical element, Ra, with atomic number 88. The atomic weight of the most abundant naturally occurring isotope is 226. Radium is a rare radioactive element found in uranium minerals to the extent of 1 part for about every 3 × 10<sup>6</sup> parts of uranium. Chemically, radium is an alkaline-earth metal having properties quite similar to those of barium. Radium is important because of its radioactive properties and is used primarily in medicine for the treatment of cancer, in atomic energy technology for the preparation of standard sources of radiation, as a source for actinium and protactinium by neutron bombardment, and in certain metallurgical and mining industries for preparing gamma-ray radiographs.
Industry:Science
A chemical element, Re, with atomic number 75 and atomic weight 186.2. Rhenium is a transition element. It is a dense metal (21.04) with the very high melting point of 3440°C (6220°F).
Industry:Science
A chemical element, S, atomic number 16, and atomic weight 32.064. The atomic weight reflects the fact that sulfur is composed of the isotopes <sup>32</sup>S (95.1%), <sup>33</sup>S (0.74%), <sup>34</sup>S (4.2%), and <sup>36</sup>S (0.016%). The ratios of the various isotopes vary slightly but measurably according to the history of the sample. By virtue of its position in the periodic table, sulfur is classified as a main-group element.
Industry:Science
A chemical element, Sr, atomic number 38, and atomic weight 87.62. Strontium is the least abundant of the alkaline-earth metals. The crust of the Earth is 0.042% strontium, making this element as abundant as chlorine and sulfur. The main ores are celestite, SrSO<sub>4</sub>, and strontianite, SrCO<sub>3</sub>.
Industry:Science
A chemical element, symbol Ag, atomic number 47, atomic mass 107.868. It is a gray-white, lustrous metal. Chemically it is one of the heavy metals and one of the noble metals; commercially it is a precious metal. Copper, silver, and gold make up group I of the periodic table of elements. Silver has been known as a metal since very ancient times; it was mentioned in the books of the Egyptian king Menes, in about 3600 <small>B</small>.<small>C</small>., who set its value at two-fifths that of gold. The chemical symbol Ag is derived from the Latin word for silver, <i>argentum</i>. Twenty-five isotopes of silver, including nine nuclear isomers, have been reported. Their atomic masses range from 102 to 117. Of the radioactive isotopes, the shortest half-life is that of <sup>114</sup>Ag, 5 s, and the longest that of <sup>108<i>m</i></sup>Ag, about 5 years. Ordinary silver is made up of the isotopes of masses 107 (52% of natural silver) and 109 (48%).
Industry:Science
