Elements on Earth

Earth s cmst extends from the surface to a depth of about 40 km (about 25 mi). Because of technical difficulties, scientists have been unable to study the inner portions of Earth as easily and as thoroughly as the crast. Nevertheless, it is believed that there is a solid core consisting mostly of iron at the center of Earth. Surrounding the core is a layer called the mantle, which consists of hot fluid containing iron, carbon, silicon, and sulfur. 

1 Which of the foUowmg series of elemental symbols lists a nonmetal, a metal, and a metalloid  

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Sodium is present in fair abundance in the sun and stars. The D lines of sodium are among the most prominent in the solar spectrum. Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth s crust it is the most abundant of the alkali group of metals. 

Searches for the element on earth have been fruitless, and it now appears that promethium is completely missing from the earth s crust. Promethium, however, has been identified in the spectrum of the star HR465 in Andromeda. This element is being formed recently near the star s surface, for no known isotope of promethium has a half-life longer than 17.7 years. Seventeen isotopes of promethium, with atomic masses from 134 to 155 are now known. Promethium-147, with a half-life of 2.6 years, is the most generally useful. Promethium-145 is the longest lived, and has a specific activity of 940 Ci/g. 

Oxygen is the most abundant element on earth The earths crust is rich in carbonate and sili cate rocks the oceans are almost entirely water and oxygen constitutes almost one fifth of the air we breathe Carbon ranks only fourteenth among the elements in natural abundance but trails only hydro gen and oxygen in its abundance in the human body It IS the chemical properties of carbon that make it uniquely suitable as the raw material forthe building blocks of life Let s find out more about those chemi cal properties... 

Potassium and sodium share the position of the seventh most abundant element on earth. Common minerals such as alums, feldspars, and micas are rich in potassium. Potassium metal, a powerful reducing agent, does not exist in nature. 

Chlorine. Chlorine, the material used to make PVC, is the 20th most common element on earth, found virtually everywhere, in rocks, oceans, plants, animals, and human bodies. It is also essential to human life. Eree chlorine is produced geothermally within the earth, and occasionally finds its way to the earth s surface in its elemental state. More usually, however, it reacts with water vapor to form hydrochloric acid. Hydrochloric acid reacts quickly with other elements and compounds, forming stable compounds (usually chloride) such as sodium chloride (common salt), magnesium chloride, and potassium chloride, all found in large quantities in seawater. 

Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

Iron, Fe, the most widely used of all the d-metals, is the most abundant element on Earth and the second most abundant metal in the Earth s crust (after aluminum). Its principal ores are the oxides hematite, Fe203, and magnetite, Fc C)4. The sulfide mineral pyrite, FeS2 (see Fig. 15.11), is widely available, but it is not used in steelmaking because the sulfur is difficult to remove. 

Phosphorus is the tenth most abundant element on Earth with an average crustal abundance of 0.1% and may be found in a wide variety of mineral phases. There are approximately 300 naturally occurring minerals in which PO4 is a required structural component. Phosphate may also be present as a trace component in many minerals either by the substitution of small quantities of POt into the crystal structure or by the adsorption of P04 onto the mineral surface (Nriagu and Moore, 1984 Slansky, 1986). 

According to Table 14-4. chlorine is also resistant to oxidation. Unlike nitrogen, however, chlorine reacts spontaneously with metals to generate salts such as NaCl and MgCl2 Thus, among abundant elements on Earth, nitrogen is uniquely stable in... 

Hydrogen combines with many other elements, including carbon. Consequently, there is quite abit of hydrogen on Earth, almost all in combination with other elements. It is the tenth most abundant element on Earth. 

We know a great deal about the nature of the universe. For instance, the element hydrogen makes up about 75% of all the mass in the universe. In terms of number, about 90% of all atoms in the universe are hydrogen atoms, and most of the rest of the atoms in the universe are helium. All the other heavier elements make up just one to two percent of the total. Interestingly, the most abundant element on Earth (in number of atoms) is oxygen (O ). Oxygen accounts for about 50% of all the elements found in the Earth s crust, and silicon, the second most abundant element, makes up about 25%. Silicon dioxide (SiO ) accounts for about 87% of the total Earth s mass. Sfiicon dioxide is the main chemical compound found in sand and rocks. 

Rubidium does not exist in its elemental metallic form in nature. However, in compound forms it is the 22nd most abundant element on Earth and, widespread over most land areas in mineral forms, is found in 310 ppm. Seawater contains only about 0.2 ppm of rubidium, which is a similar concentration to lithium. Rubidium is found in complex minerals and until recently was thought to be a rare metal. Rubidium is usually found combined with other Earth metals in several ores. The lepidolite (an ore of potassium-lithium-aluminum, with traces of rubidium) is treated with hydrochloric acid (HCl) at a high temperature, resulting in lithium chloride that is removed, leaving a residue containing about 25% rubidium. Another process uses thermochemical reductions of lithium and cesium ores that contain small amounts of rubidium chloride and then separate the metals by fractional distillation. 

The stable form of Cs-133 is the 48th most abundant element on Earth, but because it is so reactive, it is always in compound form. The Earths crust contains only about 7 ppm of Cs-133. Like the other alkali metals, it is found in mixtures of complex minerals. Its main source is the mineral pollucite (CsAlSi Og). It is also found in lepidohte, a potassium ore. Pollucite is found in Maine, South Dakota, Manitoba, and Elba and primarily in Rhodesia, South Africa. 

Cobalt is the 32nd most abundant element on Earth even though it makes up only 0.003% of the Earth s crust. It is not found in the free metallic state, despite being widely distributed in igneous rocks as minerals. Its two most common mineral ores are cobaltite (CoAsS) and erythrite [Co lAsO l ]. These ores are placed in blast furnaces to produce cobalt arsenide (COjAs), which is then treated with sulfuric acid to remove the arsenic. Finally, the product cobalt tetraoxide (Co O ) is reduced by heat with carbon (Co O + C — 3Co + 2COf resulting in cobalt metal. 

Copper is the 26th most abundant element on Earth, but it is rare to find pure metallic deposits. It is found in many different types of mineral ores, many of which are close to the surface and easy to extract. It is found in two types of ores (1) sulfide ores, such as covellite, chalcopyrite, bornite, chalcocite, and enargite and (2) oxidized ores, such as tenorite, malachite, azurite, cuprite, chrysocolla, and brochanite. 

Molybdenum is the 54th most abundant element on Earth. It is relatively rare and is found in just 126 ppm in the Earth s crust. Its major ore is molybdenite (MoS ), which is mined in Colorado in the United States and is found too in Canada, Chile, China, England, Norway, Sweden, Mexico, and Australia. Moldybdenum is also found in two less important ores wul-fenite (PbMoO ) and powellite ([Ca(MoW)0 ]. These ores are usually found in the same sites along with tin and tungsten ores. 

Technetium is the 76th most abundant element, but it is so rare that it is not found as a stable element on Earth. All of it is artificially produced. Even though natural technetium is so scarce that it is considered not to exist on Earth, it has been identified in the tight spectrum from stars. Using a spectroscope that produces unique tines for each element, scientists are able to view several types of stars. The resulting spectrographs indicate that technetium exists in the stars and thus the universe, but not on Earth as a stable element. 

Palladium is considered a rare metal, making up only about 1 part per 100 million parts of the Earth s crust. It is considered the 77th most abundant element on Earth, although it is... 

ISOTOPES There are 49 isotopes of tantalum. Only the isotope Ta-181 is stable and accounts for 99.988% of the total mass of the element on Earth. Just 0.012% of the... 

Osmium is the 80th most abundant element on Earth. As a metal, it is not found free in nature and is considered a companion metal with iridium. It is also found mixed with platinum- and nickel-bearing ores. It is recovered by treating the concentrated residue of these ores with aqua regia (a mixture of 75% HCl and 25% HNO). The high cost of refining osmium is made economically feasible by also recovering marketable amounts of platinum and nickel. 

Boron is the 38th most abundant element on Earth. It makes up about 0.001% of the Earths crust, or 10 parts per mdhon, which is about the same abundance as lead. It is not found as a free element in nature but rather in the mineral borax, which is a compound of hydrated sodium, hydrogen, and water. Borax is found in salty lakes, dry lake-beds, or alkali soils. Other naturally occurring compounds are either red crystalline or less dense, dark-brown or black powder. 

Carbon is, without a doubt, one of the most important elements on Earth. It is the major element found in over one million organic compounds and is the minor component in minerals such as carbonates of magnesium and calcium (e.g., limestone, marble, and dolomite), coral, and shells of oysters and clams. 

Lead is the 35th most abundant element on Earth. Although it has been found in its free elemental metal state, it is usually obtained from a combination of the following ores galena (PbS), anglesite (PbSO ), cerussite (PbCOj), and minum (Pb O ). Lead ores are located in Europe (Germany, Rumania, and France), Africa, Australia, Mexico, Peru, Bolivia, and Canada. The largest deposits of lead in the United States are in the states of Missouri, Kansas, Oklahoma, Colorado, and Montana. 

Although antimony is not a rare metal, it is not well known, despite having been known and used for many centuries. It is the 63rd most abundant element on Earth, and it occurs mainly as sulfide ores or in combination with the ores of other metals. The ore that is the primary source of antimony is the mineral stibnite (antimony sulfide, Sb S ). Antimony is also found in copper, silver, and lead ores. Breithauptite (NiSb) and ullmanite (NiSbS) are two ores containing nickel. Dicrasite (Ag Sb) and pyrargyrite (Ag ShS ) are silver ores containing some antimony. 

Oxygen is, without a doubt, the most essential element on Earth. It is required to support all plant and animal life, and it forms more compounds with other elements than any other element. 

Iodine is the 64th most abundant element on Earth. It occurs widely over the Earth, but never in the elemental form and never in high concentrations. 

Chemists of the early twentieth century tried to find the existence of element 85, which was given the name eka-iodine by Mendeleev in order to fill the space for the missing element in the periodic table. Astatine is the rarest of all elements on Earth and is found in only trace amounts. Less than one ounce of natural astatine exists on the Earth at any one time. There would be no astatine on Earth if it were not for the small amounts that are replenished by the radioactive decay process of uranium ore. Astatine produced by this uranium radioactive decay process soon decays, so there is no long-term build up of astatine on Earth. The isotopes of astatine have very short half-lives, and less than a gram has ever been produced for laboratory study. 

Helium is the 73rd most abundant element on Earth, but it is the second most abundant element in the universe, after hydrogen. Together, helium and hydrogen make up 99.9% of all the elements in the universe, but hehum makes up only a small trace of the elements on Earth. 

Argon is the 56th most abundant element on Earth. It is the most abundant of all the noble gases found in the atmosphere. In fact, the only source of argon is the atmosphere, where it is found at just under 1% of air by volume. 

Krypton is the 81st most abundant element on Earth and ranks seventh in abundance of the gases that make up Earths atmosphere. It ranks just above methane (CH ) in abundance in the atmosphere. Krypton is expensive to produce and thus has hmited use. The gas is captured commercially by fractional distillation of liquid air. Krypton shows up as an impurity in the residue. Along with some other gases, it is removed by filtering through activated charcoal and titanium. 

Lanthanum is the fourth most abundant of the rare-earths found on the Earth. Its abundance is 18 ppm of the Earth s crust, making it the 29th most abundant element on Earth. Its abundance is about equal to the abundance of zinc, lead, and nickel, so it is not really rare. Because the chemical and physical properties of the elements of the lanthanide series are so similar, they are quite difficult to separate. Therefore, some of them are often used together as an alloy or in compounds. 

Cerium is the 25th most abundant element on Earth. It is also the most abundant rare-earth metal in the lanthanide series. Its major ores are monazite and bastnasite. Cerium is found in the Earth s crust in 46 ppm, which is about 0.0046% of the Earth s crust. Cerium is mixed with other elements in its ores, making it difflcult to find, isolate, and identify. Its existence was unknown until about 1803... 

Praseodymium is the 41st most abundant element on Earth and is found in the ores of mona-zite, cerite, bastnasite, and allanite along with other rare-earths. Praseodymium is also the stable isotope resulting from the process of fission of some other heavy elements, such as uranium. 

Although neodymium is the 28th most abundant element on Earth, it is third in abundance of all the rare-earths. It is found in monazite, bastnasite, and allanite ores, where it is removed by heating with sulfuric acid (H SO ). Its main ore is monazite sand, which is a mixture of Ce, La, Th, Nd, Y, and small amounts of other rare-earths. Some monazite sands are composed of over 50% rare-earths by weight. Like most rare-earths, neodymium can be separated from other rare-earths by the ion-exchange process. 

Europium is the 13th most abundant of all the rare-earths and the 55th most abundant element on Earth. More europium exists on Earth than all the gold and silver deposits. Like many other rare-earths, europium is found in deposits of monazite, bastnasite, cerite, and allanite ores located in the river sands of India and Brazil and in the beach sand of Florida. It has proven difficult to separate europium from other rare-earths. Today, the ion-exchange... 

Gadohnium is the 40th most abundant element on Earth and the sixth most abundant of the rare-earths found in the Earths crust (6.4 ppm). Like many other rare-earths, gadolinium is found in monazite river sand in India and Brazil and the beach sand of Florida as well as in bastnasite ores in southern California. Similar to other rare-earths, gadolinium is recovered from its minerals by the ion-exchange process. It is also produced by nuclear fission in atomic reactors designed to produce electricity. 

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