An alkaline earth metal is the six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all sparkling, silvery-white, rather reactive metal at standard temperature and pressure.
Structurally, they have one full outer electron cell; that is, this orbital contains a complete complement of two electrons, which easily lose these elements to form a cation with charge 2, and the oxidation state 2.
All alkaline earth metals are found to occur in nature. Experiments have been made to try the synthesis of element 120, the next group member candidate, but they all have failed.
Video Alkaline earth metal
Characteristics
Chemistry
Like other groups, these family members show patterns in their electronic configurations, especially the outermost shell, which generates trends in chemical behavior:
Most of the chemistry has been observed only for the first five members of the group. Radium chemistry is not well established because of its radioactivity; thus, the presentation of the properties here is limited.
The alkaline earth metal is all silver and soft, and has a relatively low density, melting point, and boiling point. In chemical terms, all alkali metals react with halogens to form alkaline earth metal halides, all of which are ionic crystallizing compounds (except for beryllium chloride, which is covalent). All alkaline earth metals except beryllium also react with water to form highly alkaline hydroxides and, as such, must be handled with extreme caution. Heavier alkaline earth reacts harder than lighter ones. Alkali metals have the second lowest first ionization energies in periods of each periodic table due to relatively low nuclear charges and the ability to achieve the outer frame configuration is full of the loss of only two electrons. The second ionisation energy of all alkali metals is also rather low.
Beryllium is an exception: It does not react with water or steam, and its halides are covalent. If beryllium does form a compound with an ionization state 2, it will polarize a very close electron cloud very strongly and will cause a wide overlap of orbital, since beryllium has a high charge density. All compounds containing beryllium have covalent bonds. Even beryllium fluoride compounds, which are the most ionic beryllium compounds, have low melting points and low electrical conductivity when melted.
All of the alkaline earth metals have two electrons in their valence shell, so the energetically favored state of achieving a filled electron shell is the loss of two electrons to form a double-charged positive ion.
Compounds and reactions
Alkaline earth metals all react with halogens to form ionic halides, such as calcium chloride ( CaCl
2 ), and reacts with oxygen to form oxides such as strontium oxide ( SrO ). Calcium, strontium, and barium react with water to produce hydrogen and hydroxide gas respectively, and also undergo transmetalation reactions to exchange the ligands.
Physical and atom
The table below summarizes the physical and key atomic properties of the alkaline earth metals.
Nuclear stability
Of the six alkaline earth metals, beryllium, calcium, barium, and radium have at least one natural radioisotope; magnesium and strontium are not. Beryllium-7, beryllium-10, and calcium-41 are radioisotope traces; calcium-48 and barium-130 have a very long half-life and thus occur naturally on earth; and all radium isotopes are radioactive. Calcium-48 is the lightest nuclide to experience multiple beta decay. Weak calcium and barium are radioactive: calcium contains about 0.1874% cacium-41, and barium contains about 0.1062% barium-130.
Maps Alkaline earth metal
History
Etymology
Alkaline earth metals are named after their oxides, alkaline earths, whose ancient names are berylyl, magnesia, chalk, strontia, and baryta. This oxide is alkaline (alkaline) when combined with water. "Earth" is an old term applied by early chemists to non-metallic substances that are insoluble in water and resistant to heating - properties possessed by this oxide. The realization that the earth is not an element but a compound is associated with the chemist Antoine Lavoisier. In his book Traità ©  © ÃÆ' â € ° lÃÆ' © mentaire de Chimie ( Chemical Elements ) in 1789 he called them the salt-forming earth element. Later, he suggested that alkaline earth might be metal oxide, but admits that this is just a conjecture. In 1808, acting on the idea of ​​Lavoisier, Humphry Davy became the first to obtain a metal sample by electrolyzing his melting soil, thus supporting the Lavoisier hypothesis and causing the group to be called an alkaline earth metal.
Discovery
Calcite calcite and lime compounds have been known and used since prehistoric times. The same is true for beryllium beryl and emeralds. Other compounds of alkaline earth metals were discovered beginning in the early 15th century. Magnesium sulfate magnesium was first discovered in 1618 by a farmer at Epsom in England. Strontium carbonate was found in a mineral in the village of Strontian in Scotland in 1790. The last element is the least abundant: radioactive radium, extracted from uraninite in 1898.
All elements except beryllium are isolated by electrolysis of a liquid compound. Magnesium, calcium, and strontium were first produced by Humphry Davy in 1808, while beryllium was independently isolated by Friedrich WÃÆ'¶hler and Antoine Bussy in 1828 by reacting the beryllium compound with potassium. In 1910, radium was isolated as pure metal by Curie and AndrÃÆ' © -Louis Debierne also with electrolysis.
Beryllium
Beryl, a mineral containing beryllium, has been known since the days of the Ptolemaic Kingdom in Egypt. Although it was originally thought that beryl was an aluminum silicate, later beryl was found to contain an unknown element when, in 1797, Louis-Nicolas Vauquelin dissolved aluminum hydroxide from beryl in alkali. In 1828, Friedrich WÃÆ'¶hler and Antoine Bussy independently isolated this new element, beryllium, by the same method, involving the reaction of beryllium chloride with metallic potassium; This reaction is not capable of producing large beryllium ingots. It was not until 1898, when Paul Lebeau conducted an electrolysis mixture of beryllium fluoride and sodium fluoride, that a large pure beryllium sample was produced.
Magnesium
Magnesium was first produced by Sir Humphry Davy in England in 1808 using electrolysis of a mixture of magnesium and mercury oxide. Antoine Bussy prepared it in coherent form in 1831. Davy's first suggestion for a name was magnium, but the name magnesium is now used.
Calcium
Limestone has been used as a building material since 7,000 to 14,000 BC, and the kiln used for lime has been dated to 2,500 BC in Khafaja, Mesopotamia. Calcium as a substance has been known since at least the first century, since the ancient Romans were known to use calcium oxide by preparing it from lime. Calcium sulfate has been known to break broken bones since the 10th century. Calcium itself, however, was not isolated until 1808, when Humphry Davy, in the UK, used electrolysis on a mixture of lime and mercury oxide, after hearing that JÃÆ'¶ns Jakob Berzelius had prepared calcium amalgam from lime electrolysis in mercury.
Strontium
In 1790, physician Adair Crawford, who had worked with barium, noticed that the Strontian ore showed different properties than any other suspected barium ore. Therefore, he concluded that this ore contained a new mineral, named after strontites in 1793 by Thomas Charles Hope, a professor of chemistry at the University of Glasgow, who confirmed the discovery of Crawford. Strontium was finally isolated in 1808 by Sir Humphry Davy with electrolysis of a mixture of strontium chloride and mercury oxide. The discovery was announced by Davy on June 30, 1808, at a lecture at the Royal Society.
Barium
Barite, a mineral containing barium, was first recognized to contain a new element in 1774 by Carl Scheele, although he was able to isolate only barium oxide. Barium oxide was isolated again two years later by Johan Gottlieb Gahn. Later in the 18th century, William Withering noticed the heavy minerals in the main mine of Cumberland, which is now known to contain barium. Barium itself was finally isolated in 1808 when Sir Humphry Davy used electrolysis with molten salt, and Davy named the element barium after baryta. Later, Robert Bunsen and Augustus Matthiessen isolated the pure barium by electrolyzing a mixture of barium chloride and ammonium chloride.
Radium
When studying uraninite, on December 21, 1898, Marie and Pierre Curie discovered that, even after uranium had decomposed, the material that was made was still radioactive. The material behaves somewhat similar to a barium compound, although some properties, such as the color of flame test and spectral lines, are much different. They announced the discovery of a new element on December 26, 1898 to the French Academy of Sciences. Radium was named in 1899 from the word radius , which means ray , as the radium power emitted in the form of rays.
Genesis
Beryllium occurs in the Earth's crust at concentrations of two to six parts per million (ppm), many of which are in soil, where it has a concentration of six ppm. Beryllium is one of the rarest elements in seawater, even more scarce than elements such as scandium, with a concentration of 0.2 parts per trillion. However, in freshwater, beryllium is somewhat more common, with a concentration of 0.1 parts per billion.
Magnesium and calcium are very common in the earth's crust, with the most abundant fifth elemental calcium, and the eighth magnesium. None of the alkaline earth metals are found in their elemental states, but magnesium and calcium are found in many rocks and minerals: magnesium in carnallite, magnesite, and dolomite; and calcium in limestone, limestone, gypsum, and anhydride.
Strontium is the fifteenth most abundant element in the Earth's crust. Most strontium is found in celestite and strontianite minerals. Barium is slightly less common, many in mineral barrels.
Radium, which is a product of uranium decay, is found in all ores containing uranium. Because of the relatively short half-life, radium from the early Earth's history has decayed, and today's samples are all from a much slower decay of uranium.
Production
Most beryllium is extracted from beryllium hydroxide. One method of production is sintering, which is done by mixing beryl, sodium fluorosilicate, and soda at high temperatures to form sodium fluoroberyllate, aluminum oxide, and silicon dioxide. A solution of sodium fluoroberyllate and sodium hydroxide in water is then used to form beryllium hydroxide by precipitation. Alternatively, in the melting method, the beryl powder is heated to a high temperature, cooled with water, then heated slightly in sulfuric acid, eventually producing beryllium hydroxide. Beryllium hydroxide from both methods then produces beryllium fluoride and beryllium chloride through a rather long process. Electrolysis or heating of these compounds can then produce beryllium.
In general, strontium carbonate is extracted from celestite minerals by two methods: by releasing celestite with sodium carbonate, or in a more complicated way involving coal.
To produce barium, barite ore is separated from quartz, sometimes by flotation method, yielding relatively pure barite. Carbon is then used to reduce barrels to barium sulfide, which is dissolved with other elements to form other compounds, such as barium nitrate. This in turn is thermally decompressed into barium oxide, which eventually produces a pure barium after reaction with aluminum. The most important barium supplier is China, which produces more than 50% of world supply.
Apps
Beryllium is mostly used for military applications, but there are other uses of beryllium, as well. In electronics, beryllium is used as p-dopant type in some semiconductors, and beryllium oxide is used as an electrical insulator and high-powered heat conductor. Due to its light weight and other properties, beryllium is also used in mechanics when stiffness, lightness, and dimensional stability are required over a wide temperature range.
Magnesium has many different uses. One of its most common uses is in the industry, where it has many structural advantages over other materials such as aluminum, although this use has fallen off its recent disposition due to its highly flammable magnesium. Magnesium is also often mixed with aluminum or zinc to form materials with more desirable properties than pure metal. Magnesium has many other uses in industrial applications, such as having a role in iron and steel production, and titanium production.
Calcium also has many uses. One of its uses is as a reducing agent in the separation of other metals from ores, such as uranium. It is also used in the production of many metal alloys, such as aluminum alloys and copper, and is also used to oxidize alloys as well. Calcium also has a role in cheese, mortar, and cement making.
Strontium and barium do not have many applications such as lighter alkaline earth metals, but still have a use. Strontium carbonate is often used in the manufacture of red fireworks, and pure strontium is used in studies of neurotransmitter release in neurons. Barium has some use in vacuum tubes to remove gas, and barium sulfate has many uses in the petroleum industry, as well as other industries.
Because of its radioactivity, radium no longer has many applications, but it is used to have many. Radium used is often used in luminous paint, although this use is terminated after the worker gets sick. When people think that radioactivity is a good thing, radium is used to add to drinking water, toothpaste, and many other products, although they are also not used anymore because of their health effects. Radium is no longer used for its radioactive properties, because there is a stronger, safer emitter than radium.
Biological roles and precautions
Magnesium and calcium are everywhere and important for all living organisms that are known. They are involved in more than one role, with, for example, magnesium or calcium ion pumps acting in some cellular processes, magnesium acts as an active center in some enzymes, and calcium salts take a structural role, especially in bone.
Strontium plays an important role in marine aquatic life, especially hard corals, which use strontium to build up their exoskeleton. This and barium have several uses in medicine, such as "barium food" in radiographic imaging, while strontium compounds are used in some toothpastes. Excessive amounts of strontium-90 are toxic because radioactivity and strontium-90 mimic calcium and can then kill.
Beryllium and radium, however, are toxic. Berillium low beryllium solubility means rarely available for biological systems; it has no known role in living organisms and, when encountered by them, is usually very toxic. Radium has low availability and is highly radioactive, making it toxic to life.
Extensions
The next alkaline earth metal after radium is considered element 120, although this may not be true because of its relativistic effect. The 120 element synthesis was first attempted in March 2007, when a team at the Nuclear Reaction Flerov Laboratory in Dubna bombarded plutonium-244 with a 58-iron ion; However, no atoms are produced, leading to a limit of 400 fb for cross sections on the energy being studied. In April 2007, a team at GSI sought to fabricate element 120 by bombarding uranium-238 with nickel-64, although no atoms were detected, leading to a 1.6 bpb limit for the reaction. Synthesis is again attempted at higher sensitivity, although no atoms are detected. Other reactions have been tried, even though all have failed.
Chemical element 120 is estimated to be closer to calcium or strontium, not barium or radium. This is unusual because the periodic trend will predict the 120 element to be more reactive than barium and radium. This decreased reactivity is due to the expected energy of the valence electrons of element 120, increasing the ionisation energy of the element 120 and decreasing the radius of metal and ionic.
Although a simple extrapolation would place the element 170 as the next member of this series, the calculations show that the next element of this series may actually be the 166 element.
Note
References
Bibliography
- Sunday, Mary Elvira; Leichester, Henry M. (1968). Invention of the Elements . Easton, PA: Journal of Chemistry Education. LCCCN 68-15217.
Further reading
- Group 2 - Alkaline Earth Metal, Royal Chemistry Society.
- Hogan, C.Michael. 2010. Calcium . eds. A. Jorgensen, C. Cleveland. The Earth Encyclopedia. National Council for Science and the Environment.
- Maguire, Michael E. "Alkaline Earth Metals." Chemicals: Foundations and Applications . Ed. J. J. Lagowski. Vol. 1. New York: Macmillan Reference USA, 2004. 33-34. 4 vols. Gale Virtual Reference Library. Thomson Gale.
- Silberberg, M.S., Chemistry: Molecular Properties of Materials and Changes (3e ÃÆ' Â © dition, McGraw-Hill 2009)
- Petrucci R.H., Harwood W.S. et Herring F.G., General Chemistry (8e ÃÆ' Â © dition, Prentice-Hall 2002)
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