In modernIUPAC notation, it is calledgroup 14. In the field ofsemiconductor physics, it is still universally calledgroup IV. The group is also known as thetetrels (from the Greek wordtetra, which means four), stemming from the Roman numeral IV in the group name, or (not coincidentally) from the fact that these elements have fourvalence electrons (see below). They are also known as thecrystallogens[1] oradamantogens.[2]
Like other groups, the members of this family show patterns inelectron configuration, especially in the outermost shells, resulting in trends in chemical behavior:
Each of theelements in this group has 4electrons in its outershell. An isolated, neutral group 14 atom has the s2 p2 configuration in the ground state. These elements, especiallycarbon andsilicon, have a strong propensity forcovalent bonding, which usually brings the outer shellto eight electrons. Bonds in these elements often lead tohybridisation where distincts and p characters of the orbitals are erased. Forsingle bonds, a typical arrangement hasfour pairs of sp3 electrons, although other cases exist too, such as three sp2 pairs ingraphene and graphite. Double bonds are characteristic for carbon (alkenes,CO2...); the same forπ-systems in general. The tendency to lose electrons increases as the size of theatom increases, as it does with increasing atomic number.Carbon alone forms negativeions, in the form ofcarbide (C4−) ions.Silicon andgermanium, bothmetalloids, each can form +4 ions.Tin andlead both aremetals, while flerovium is a synthetic,radioactive (its half life is very short, only 1.9 seconds) element that may have a fewnoble gas-like properties, though it is still most likely a post-transition metal. Tin and lead are both capable of forming +2 ions. Although tin is chemically a metal,its α allotrope looks more like germanium than like a metal and it is a poor electric conductor.
Among main group (groups 1, 2, 13–17) alkyl derivatives QRn, wheren is the standard bonding number for Q (seelambda convention), the group 14 derivatives QR4 are notable in being electron-precise: they are neither electron-deficient (having fewer electrons than an octet and tending to be Lewis acidic at Q and usually existing as oligomeric clusters or adducts with Lewis bases) nor electron-excessive (having lone pair(s) at Q and tending to be Lewis basic at Q). As a result, the group 14 alkyls have low chemical reactivity relative to the alkyl derivatives of other groups. In the case of carbon, the high bond dissociation energy of theC–C bond and lack of electronegativity difference between the central atom and the alkyl ligands render the saturated alkyl derivatives, thealkanes, particularly inert.[3]
Germanium forms five hydrides. The first two germanium hydrides areGeH4 andGe2H6. Germanium forms tetrahalides with all halogens except astatine and forms dihalides with all halogens except bromine and astatine. Germanium bonds to all natural single chalcogens except polonium, and forms dioxides, disulfides, and diselenides.Germanium nitride has the formula Ge3N4.[7]
Tin forms two hydrides:SnH4 andSn2H6. Tin forms dihalides and tetrahalides with all halogens except astatine. Tin forms monochalcogenides with naturally occurring chalcogens except polonium, and forms dichalcogenides with naturally occurring chalcogens except polonium and tellurium.[8]
Lead forms one hydride, which has the formulaPbH4. Lead forms dihalides and tetrahalides with fluorine and chlorine, and formsa dibromide anda diiodide, although the tetrabromide and tetraiodide of lead are unstable. Lead formsfour oxides,a sulfide,a selenide, anda telluride.[9]
Theboiling points of the carbon group tend to get lower with the heavier elements. Atstandard pressure, carbon, the lightest carbon group element,sublimes at 3825 °C. Silicon's boiling point is 3265 °C, germanium's is 2833 °C, tin's is 2602 °C, and lead's is 1749 °C. Flerovium is predicted to boil at −60 °C.[11][12] Themelting points of the carbon group elements have roughly the same trend as their boiling points. Silicon melts at 1414 °C, germanium melts at 939 °C, tin melts at 232 °C, and lead melts at 328 °C.[13]
Carbon's crystal structure ishexagonal; at high pressures and temperatures it formsdiamond (see below). Silicon and germanium havediamond cubic crystal structures, as does tin at low temperatures (below 13.2 °C). Tin at room temperature has atetragonal crystal structure. Lead has aface-centered cubic crystal structure.[13]
Thedensities of the carbon group elements tend to increase with increasing atomic number. Carbon has a density of 2.26 g·cm−3; silicon, 2.33 g·cm−3; germanium, 5.32 g·cm−3; tin, 7.26 g·cm−3; lead, 11.3 g·cm−3.[13]
Theatomic radii of the carbon group elements tend to increase with increasing atomic number. Carbon's atomic radius is 77picometers, silicon's is 118 picometers, germanium's is 123 picometers, tin's is 141 picometers, and lead's is 175 picometers.[13]
Carbon has multipleallotropes. The most common isgraphite, which is carbon in the form of stacked sheets. Another form of carbon isdiamond, but this is relatively rare.Amorphous carbon is a third allotrope of carbon; it is a component ofsoot. Another allotrope of carbon is afullerene, which has the form of sheets of carbon atoms folded into a sphere. A fifth allotrope of carbon, discovered in 2003, is calledgraphene, and is in the form of a layer of carbon atoms arranged in a honeycomb-shaped formation.[6][14][15]
Silicon has two known allotropes that exist at room temperature. These allotropes are known as the amorphous and the crystalline allotropes. The amorphous allotrope is a brown powder. The crystalline allotrope is gray and has a metallicluster.[16]
Tin has two allotropes: α-tin, also known as gray tin, and β-tin. Tin is typically found in the β-tin form, a silvery metal. However, at standard pressure, β-tin converts to α-tin, a gray powder, at temperatures below 13.2 °C (55.8 °F). This can cause tin objects in cold temperatures to crumble to gray powder in a process known astin pest or tin rot.[6][17]
At least two of the carbon group elements (tin and lead) havemagic nuclei, meaning that these elements are more common and more stable than elements that do not have a magic nucleus.[17]
23isotopes of silicon have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay ofactinides, and viaspallation in the upper atmosphere. Silicon-34 also occurs naturally as the result of radioactive decay of actinides.[18]
32isotopes of germanium have been discovered. Five of these are naturally occurring. The most common is the stable germanium-74, followed by stable germanium-72, stable germanium-70, and stable germanium-73. Germanium-76 is aprimordial radioisotope.[18]
40isotopes of tin have been discovered. 14 of these occur in nature. The most common is tin-120, followed by tin-118, tin-116, tin-119, tin-117, tin-124, tin-122, tin-112, and tin-114: all of these are stable. Tin also has four radioisotopes that occur as the result of the radioactive decay of uranium. These isotopes are tin-121, tin-123, tin-125, and tin-126.[18]
38isotopes of lead have been discovered. 9 of these are naturally occurring. The most common isotope is lead-208, followed by lead-206, lead-207, and lead-204: all of these are stable. 5 isotopes of lead occur from the radioactive decay of uranium and thorium. These isotopes are lead-209, lead-210, lead-211, lead-212 and lead-214.[18]
6isotopes of flerovium (flerovium-284, flerovium-285, flerovium-286, flerovium-287, flerovium-288, and flerovium-289) have been discovered, all from human synthesis. Flerovium's most stable isotope is flerovium-289, which has a half-life of 2.6 seconds.[18]
Carbon accumulates as the result ofstellar fusion in most stars, even small ones.[17] Carbon is present in the Earth's crust in concentrations of 480 parts per million, and is present inseawater at concentrations of 28 parts per million. Carbon is present in the atmosphere in the form ofcarbon monoxide,carbon dioxide, andmethane. Carbon is a key constituent ofcarbonate minerals, and is inhydrogen carbonate, which is common in seawater. Carbon forms 22.8% of a typical human.[18]
Silicon is present in the Earth's crust at concentrations of 28%, making it the second most abundant element there. Silicon's concentration in seawater can vary from 30 parts per billion on the surface of the ocean to 2000 parts per billion deeper down. Silicon dust occurs in trace amounts in Earth's atmosphere.Silicate minerals are the most common type of mineral on earth. Silicon makes up 14.3 parts per million of the human body on average.[18] Only the largest stars produce silicon via stellar fusion.[17]
Germanium makes up 2 parts per million of the Earth's crust, making it the 52nd most abundant element there. On average, germanium makes up 1 part per million ofsoil. Germanium makes up 0.5 parts per trillion of seawater.Organogermanium compounds are also found in seawater. Germanium occurs in the human body at concentrations of 71.4 parts per billion. Germanium has been found to exist in some very faraway stars.[18]
Tin makes up 2 parts per million of the Earth's crust, making it the 49th most abundant element there. On average, tin makes up 1 part per million of soil. Tin exists in seawater at concentrations of 4 parts per trillion. Tin makes up 428 parts per billion of the human body.Tin(IV) oxide occurs at concentrations of 0.1 to 300 parts per million in soils.[18] Tin also occurs in concentrations of one part per thousand inigneous rocks.[19]
Lead makes up 14 parts per million of the Earth's crust, making it the 36th most abundant element there. On average, lead makes up 23 parts per million of soil, but the concentration can reach 20000 parts per million (2 percent) near old lead mines. Lead exists in seawater at concentrations of 2 parts per trillion. Lead makes up 1.7 parts per million of the human body by weight. Human activity releases more lead into the environment than any other metal.[18]
Flerovium doesn't occur in nature at all, so it only exists inparticle accelerators with a few atoms at a time.[18]
Silicon as silica in the form of rock crystal 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 thePhoenicians. Many of the naturally occurring compounds orsilicate minerals were used in various kinds of mortar for construction of dwellings by the earliest people.
The origins of tin seem to be lost in history. It appears that bronzes, which are alloys of copper and tin, were used by prehistoric man some time before the pure metal 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 theScilly Isles and Cornwall in the British Isles,[21] where mining of the metal dates from about 300–200 BCE. Tin mines were operating in both the Inca and Aztec areas of South and Central America before the Spanish conquest.
Lead is mentioned often in early Biblical accounts. TheBabylonians used the metal as plates on which to record inscriptions. TheRomans used 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 ofAugustus Caesar. The compound known aswhite lead was apparently prepared as a decorative pigment at least as early as 200 BCE.
Germanium is one of three elements the existence of which was predicted in 1869 by the Russian chemistDmitri Mendeleev when he first devised his periodic table. However, the element was not actually discovered for some time. In September 1885, a miner discovered a mineral sample in a silver mine and gave it to the mine manager, who determined that it was a new mineral and sent the mineral toClemens A. Winkler. Winkler realized that the sample was 75% silver, 18% sulfur, and 7% of an undiscovered element. After several months, Winkler isolated the element and determined that it was element 32.[18]
The first attempt to discover flerovium (then referred to as "element 114") was in 1969, at theJoint Institute for Nuclear Research, but it was unsuccessful. In 1977, researchers at the Joint Institute for Nuclear Research bombardedplutonium-244 atoms withcalcium-48, but were again unsuccessful. This nuclear reaction was repeated in 1998, this time successfully.[18]
Silicon dioxide has a wide variety of applications, includingtoothpaste, construction fillers, and silica is a major component ofglass. 50% of pure silicon is devoted to the manufacture of metalalloys. 45% of silicon is devoted to the manufacture ofsilicones. Silicon is also commonly used insemiconductors since the 1950s.[17][22]
Germanium was used in semiconductors until the 1950s, when it was replaced by silicon.[17] Radiation detectors contain germanium.Germanium dioxide is used infiber optics and wide-angle camera lenses. A small amount of germanium mixed withsilver can make silvertarnish-proof. The resulting alloy is known asargentium sterling silver.[18]
80% of all lead produced goes intolead–acid batteries. Other applications for lead include weights, pigments, and shielding against radioactive materials. Lead was historically used in gasoline in the form oftetraethyllead, but this application has been discontinued due to concerns of toxicity.[23]
Silicon can be produced by heating silica with carbon.[22]
There are some germanium ores, such asgermanite, but these are not mined on account of being rare. Instead, germanium is extracted from the ores of metals such aszinc. In Russia andChina, germanium is also separated from coal deposits. Germanium-containing ores are first treated withchlorine to formgermanium tetrachloride, which is mixed with hydrogen gas. Then the germanium is further refined byzone refining. Roughly 140 metric tons of germanium are produced each year.[18]
Mines output 300,000 metric tons of tin each year. China,Indonesia,Peru,Bolivia, and Brazil are the main producers of tin. The method by which tin is produced is to heat the tin mineralcassiterite (SnO2) withcoke.[18]
The most commonly mined lead ore isgalena (lead sulfide). 4 million metric tons of lead are newly mined each year, mostly in China,Australia, theUnited States, and Peru. The ores are mixed with coke andlimestone androasted to produce pure lead. Most lead is recycled fromlead batteries. The total amount of lead ever mined by humans amounts to 350 million metric tons.[18]
Carbon is a key element to all known life. It is in all organic compounds, for example,DNA,steroids, andproteins.[6] Carbon's importance to life is primarily due to its ability to form numerous bonds with other elements.[17] There are 16 kilograms of carbon in a typical 70-kilogram human.[18]
Silicon-based life's feasibility is commonly discussed. However, it is less able than carbon to form elaborate rings and chains.[6] Silicon in the form ofsilicon dioxide is used bydiatoms andsea sponges to form theircell walls andskeletons. Silicon is essential forbone growth in chickens and rats and may also be essential in humans. Humans consume on average between 20 and 1200milligrams of silicon per day, mostly fromcereals. There is 1 gram of silicon in a typical 70-kilogram human.[18]
A biological role for germanium is not known, although it does stimulatemetabolism. In 1980, germanium was reported byKazuhiko Asai to benefit health, but the claim has not been proven. Some plants take up germanium from the soil in the form ofgermanium oxide.[clarification needed] These plants, which includegrains andvegetables contain roughly 0.05 parts per million of germanium. The estimated human intake of germanium is 1 milligram per day. There are 5 milligrams of germanium in a typical 70-kilogram human.[18]
Tin has been shown to be essential for proper growth in rats, but there is, as of 2013, no evidence to indicate that humans need tin in their diet. Plants do not require tin. However, plants do collect tin in theirroots.Wheat andmaize contain 7 and 3 parts per million respectively. However, the level of tin in plants can reach 2000 parts per million if the plants are near a tinsmelter. On average, humans consume 0.3 milligrams of tin per day. There are 30 milligrams of tin in a typical 70-kilogram human.[18]
Lead has no known biological role, and is in fact highlytoxic, but somemicrobes are able to survive in lead-contaminated environments. Some plants, such ascucumbers contain up to tens of parts per million of lead. There are 120 milligrams of lead in a typical 70-kilogram human.[18]
Flerovium has no biological role and instead is found and made only in particle accelerators.
Elemental carbon is not generally toxic, but many of its compounds are, such ascarbon monoxide andhydrogen cyanide. However, carbon dust can be dangerous because it lodges in the lungs in a manner similar toasbestos.[18]
Silicon minerals are not typically poisonous. However, silicon dioxide dust, such as that emitted byvolcanoes can cause adverse health effects if it enters the lungs.[17]
Some tin compounds are toxic to ingest, but most inorganic compounds of tin are considered nontoxic. Organic tin compounds, such astrimethyltin andtriethyltin are highly toxic, and can disrupt metabolic processes inside cells.[18]
