Iron forms compounds in a wide range of oxidation states, −2 to +7. Iron shares many properties of other transition metals, including the other group 8 elements, ruthenium and osmium. Ĭhemically, the most common oxidation states of iron are iron(II) and iron(III). Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. To maintain the necessary levels, human iron metabolism requires a minimum of iron in the diet. These two proteins play essential roles in vertebrate metabolism, respectively oxygen transport by blood and oxygen storage in muscles. The body of an adult human contains about 4 grams (0.005% body weight) of iron, mostly in hemoglobin and myoglobin. Although iron readily reacts, high purity iron, called electrolytic iron, has better corrosion resistance. Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion. However, iron reacts readily with oxygen and water to give brown to black hydrated iron oxides, commonly known as rust. Pristine and smooth pure iron surfaces are mirror-like silvery-gray. The iron and steel industry is thus very important economically, and iron is the cheapest metal, with a price of a few dollars per kilogram or per pound (see Metal#uses). In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels, are by far the most common industrial metals, because of their mechanical properties and low cost. That event is considered the transition from the Bronze Age to the Iron Age. Humans started to master that process in Eurasia during the 2nd millennium BCE and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching 1,500 ☌ (2,730 ☏) or higher, about 500 ☌ (932 ☏) higher than that required to smelt copper. In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. It is the fourth most common element in the Earth's crust. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is a metal that belongs to the first transition series and group 8 of the periodic table. "Keep me informed of any new developments.Iron ( / ˈ aɪ ər n/) is a chemical element with symbol Fe (from Latin: ferrum) and atomic number 26. I'll alert the base commander and go from there." "The nearest naval facility is at Trujillo. "I will, I promise you," Miller said grimly. Their plane isn't scheduled to land in Lima for another four hours." "Not possible," Chaco replied helplessly. "All we need now," he muttered to himself, "are two dead archaeologists in the pool." He broke contact with Chaco and hurried back to the silent group of students, who were staring down into the sinkhole with dread. "Can you send the dive team ahead by helicopter?" asked Miller. "A helicopter" she announced excitedly, pointing in a westerly direction through the tops of the trees. She cupped her hands to her ears and turned back and forth like a radar antenna. One of the female students heard it first. But this was South America and speed was seldom a priority. Chaco helplessly shared Miller's anxiety over the slow response time. It was impossible for them to airlift the dive team and their equipment to the sinkhole before sundown. Their water escape and recovery team was on a training mission far to the south of Peru near the Chilean border. In a voice frantic with desperation, Chaco had informed him that the Peruvian navy was caught unprepared for an emergency. A minute later a turquoise helicopter with the letters NUMA painted on its sides swept into view. The faint thumping sound of a rotor blade beating the air came toward them, growing louder with each passing moment. In an expectant hush everyone around the rim of the pool listened. "They'll come through," offered Chaco in a hollow tone. "They planned to resurface after thirty minutes." "Keep me informed of any new developments."Ĭhaco caught his breath, closed his eyes for a second. Can you arrange to have a dive rescue team rushed to the sinkhole?" It obviously didn't have the markings of the Peruvian navy. Where had it come from? Miller wondered, his spirits rising.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |