- Carbon group
The carbon group is group 14 (
IUPACstyle) in the periodic table. Once also known as the tetrels (from Latin "tetra", four), stemming from the earlier naming convention of this group as Group IVA. The group consists of carbon(C), silicon(Si), germanium(Ge), tin(Sn), lead(Pb), and ununquadium(Uuq).
Each of the elements in this group has 4
electrons in its outer energy level. The last orbital of all these elements is the p2 orbital. In most cases, the elements share their electrons. The tendency to lose electrons increases as the size of the atomincreases, as it does with increasing atomic number. Carbonalone forms negative ions, in the form of carbide(C4−) ions. Siliconand germanium, both metalloids, each can form +4 ions. Tinand leadboth are metals while unquadium is a synthetic shortlived radioactivemetal.
Except for germanium, all of these elements are familiar in daily life either as the pure element or in the form of
compounds. However, except for silicon, none of these elements are particularly plentiful in the Earth’s crust. Carbon forms an almost infinite variety of compounds, in both the plant and animal kingdoms. Silicon and silicate minerals are fundamental components of the Earth’s crust; silica ( silicon dioxide) is sand. Tin and lead, although with very low abundances in the crust, are nevertheless common in everyday life. They occur in highly concentrated mineral deposits, can be obtained easily in the metallic state from those minerals, and are useful as metals and as alloys in many applications. Germanium, on the other hand, forms few characteristic minerals and is most commonly found only in small concentrations in association with the mineral zinc blendeand in coals. Although germanium is indeed one of the rarer elements, it assumed importance upon recognition of its properties as a semiconductor.
Carbon, tin, and lead, are a few of the elements well known in the ancient world - together with sulfur, iron, copper, mercury, silver, and gold. Carbonas an element was discovered by the first man to handle charcoal from his fire. Modern carbon chemistry dates from the development of coals, petroleum, and natural gas as fuels and from the elucidation of synthetic organic chemistry, both substantially developed since the 1800s.
Amorphous elemental silicon was first obtained pure in 1824 by the Swedish chemist
Jöns Jacob Berzelius; impure silicon had already been obtained in 1811. Crystalline elemental silicon was not prepared until 1854, when it was obtained as a product of electrolysis. In the form of rock crystal, however, silicon was familiar to the predynastic Egyptians, who used it for beads and small vases; to the early Chinese; and probably to many others of the ancients. The manufacture of glass containing silica was carried out both by the Egyptians — at least as early as 1500 BCE — and by the Phoenicians. Certainly, many of the naturally occurring compounds called silicates were used in various kinds of mortar for construction of dwellings by the earliest people.
Germanium is one of three elements the existence of which was predicted in 1871 by the Russian chemist
Dmitry Mendeleyevwhen he first devised his periodic table. Not until 1886, however, was germanium identified as one of the elements in a newly found mineral.
The origins of tin also are lost in antiquity. Apparently,
bronzes, which are copper–tin alloys, were used by man in prehistory long before pure tin metal itself was isolated. Bronzes were common in early Mesopotamia, the Indus Valley, Egypt, Crete, Israel, and Peru. Much of the tin used by the early Mediterranean peoples apparently came from the Scilly Islands and from Cornwallin the British Isles, where tin mining dates to at least 300–200 BCE. Tin mines were operating in both the Inca and Aztec domains of South and Central Americabefore the Spanish conquest.
Lead is mentioned often in early Biblical accounts. The
Babyloniansused the metal as plates on which to record inscriptions. The Romansused it for tablets, water pipes, coins, and even cooking utensils; indeed, as a result of the last use, lead poisoning was recognized in the time of Augustus Caesar. The compound known as white lead was apparently prepared as a decorative pigment at least as early as 200 BCE. Modern developments date to the exploitation in the late 1700s of deposits in the Missouri–Kansas–Oklahoma area in the United States.
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