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第十四章 碳族元素 Chapter 14 The carbon family elements

第十四章 碳族元素 Chapter 14 The carbon family elements. Carbon (C) Silicon (Si) Germanium (Ge) Stannum (Sn) Plumbum (Pb). Tin. Lead. §14-1 Carbon and its compounds 一、 General properties 1. 根据 σ 键的数目 , 碳可采取 sp 2 、 sp 3 杂化 , 其最大配 位数为 4 2. 由于碳碳单键的键能特别大 , 所以 C—C 键非常稳定 , 具有形成均链的倾向

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第十四章 碳族元素 Chapter 14 The carbon family elements

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  1. 第十四章 碳族元素Chapter 14 The carbon family elements Carbon (C)Silicon (Si) Germanium (Ge)Stannum (Sn) Plumbum (Pb) Tin Lead

  2. §14-1Carbon and its compounds • 一、General properties • 1. 根据σ键的数目,碳可采取sp2、sp3杂化,其最大配 • 位数为4 • 2. 由于碳碳单键的键能特别大,所以C—C键非常稳定 • ,具有形成均链的倾向 • 从碳到氮的单键键能的突减，是由于氮原子非键电 • 子对排斥的缘故。

  3. 二、Simple substance • 1. 在第二周期中，氟、氧、和氮都以双原子分子存在 • — F2、O2和N2；而碳存在多聚物，其理由为: O2和N2 • 的多重键要比σ单键(均键)强得多 • 2. Allotropes: diamond graphite fullerenecarbin (carbon fibers) • (1) 熵 Scarbin > Sgraphite > Sdiamond • (2) dc-c (nm): diamond > graphite > carbin E (kJ·mol1) 494 ＞210 + 210, 946 ＞250 +250+250 E (kJ·mol1) 627 ＜374 + 374

  4. (3) Cgraphite Cdiamond ∆H > 0 ∆S < 0 • 根据平衡,需要高压6e9—1e10Pa，(because of • the insignificant reduction of volume)，升高温度 • 不利于平衡的移动,但为了达到该过程可以接受的速率 • ,反应温度大约在2000℃，近来已发明一种低压生产 • 金刚石的方法:把金刚石晶种(seed)放在气态碳氢化合 • 物( 甲烷methane, ethane )中,温度升高到1000℃,可 • 以得到金刚石粉末或者crystal whiskers • CVD technique for diamond growth

  5. Due to its combination of unique physical properties diamond is an outstanding material. Besides its unrivaled hardness diamond exhibits ultrabroadband transparancy ranging from deep UV to the microwave regime, and a thermal conductivity at room temperature which is higher than that of any other material. The excellent mechanical, thermal, optical and insulating properties of diamond became accessible through the advent of low pressure Chemical Vapour Deposition (CVD) techniques which allow diamond in the form of extended films and free-standing wafers to be fabricated. The fundamental problem of diamond synthesis is the allotropic nature of carbon. Under ordinary conditions graphite, not diamond, is the thermodynamically stable crystalline phase of carbon. Hence, the main requirement of diamond CVD is to deposit carbon and simultaneously suppress the formation of graphitic sp2-bonds. This can be realized by establishing high concentrations of non-diamond carbon etchants such as atomic hydrogen. Usually, those conditions are achieved by admixing large amounts of hydrogen to the process gas and by activating the gas either thermally or by a plasma.  

  6. (4) C60 • 由12个五边形和20个六边形组成,每个该原子以sp2 • 杂化轨道与相邻的三个碳原子相连，剩余的p轨道在 • C60球壳的外围和内腔形成球面π键,从而具有芳香性 • 欧拉方程：面数(F) + 顶点数(V) = 棱数(E) + 2 • a. structure:根据欧拉定理，通过12个五边形和数 • 个六边形的连接可以形成封闭的多面体结构 • C60为第一个五边形间互不相邻的碳笼 • 不存在六边形的最小碳笼为C20

  7. 32个面，60个顶点，90条棱 12个正五边形和20个正六边形 F + V = E + 2

  8. Fullerene Discoverers Win Chemistry Nobel The Nobel Prize in chemistry was awarded today to two Americans and one British researcher for their discovery of fullerenes, a new class of all-carbon molecules shaped like hollow balls. The researchers, Richard E. Smalley and Robert F. Curl Jr. of Rice University in Houston, and Harold W. Kroto of the University of Sussex in Brighton, United Kingdom, made their discovery in 1985 in Smalley's lab at Rice while working together to study how carbon atoms cluster. "The award is richly deserved," says Robert Haddon, a fullerene chemist at Lucent Technologies' Bell Labs in Murray Hill, New Jersey. "It led to a totally new field of chemistry." Today, fullerenes--which are popularly known as buckyballs--are being investigated for everything from new superconductors and three-dimensional polymers, to catalysts and optical materials, although they have yet to spawn any commercial applications. Before the group's discovery, crystalline carbon was thought to adopt only a handful of different molecular architectures, including those found in diamond and graphite. But the researchers discovered that sheets of carbon atoms arranged in a pattern of hexagons and pentagons can curl up and ultimately close to form hollow cages. And because the number of atoms in the cage can vary, an almost infinite number of fullerene shapes may exist.

  9. The Platonic Polydedra: f=2+e-v Tetrahedron CubeOctahedronDodecahedronIcosahedron • Triangles. The interior angle of an equilateral triangle is 60 degrees. Thus on a regular polyhedron, only 3, 4, or 5 triangles can meet a vertex. If there were more than 6 their angles would add up to at least 360 degrees which they can't. Consider the possibilities: • 3 triangles meet at each vertex. This gives rise to a Tetrahedron. • 4 triangles meet at each vertex. This gives rise to an Octahedron. • 5 triangles meet at each vertex. This gives rise to an Icosahedron • Squares. Since the interior angle of a square is 90 degrees, at most three squares can meet at a vertex. This is indeed possible and it gives rise to a hexahedron or cube. • Pentagons. As in the case of cubes, the only possibility is that three pentagons meet at a vertex. This gives rise to a Dodecahedron. • Hexagons or regular polygons with more than six sides cannot form the faces of a regular polyhedron since their interior angles are at least 120 degrees.

  10. b. properties: 科学家认为C60将是21世纪的重要 • 材料 • (i) C60分子具有球形的芳香性,可以合成C60F2 ，作 • 为超级润滑剂 • (ii) C60笼内可以填入金属原子而形成超原子分子, • 作为新型催化剂或催化剂载体，具有超导性 • (iii) C60晶体有金属光泽，其微晶体粉末呈黄色， • 易溶于苯，其苯溶液呈紫红色。C60分子特别稳定，进 • 行化学反应时，C60始终是一个整体

  11. Types of carbon nanotubes: Single-walled • The (n,m) nanotube naming scheme can be thought of as a vector (Ch) in an infinite graphene sheet that describes how to "roll up" the graphene sheet to make the nanotube. T denotes the tube axis, and a1 and a2 are the unit vectors of graphene in real space.

  12. For a given (n,m) nanotube, if 2n + m=3q (where q is an integer), then the nanotube is metallic, otherwise the nanotube is a semiconductor. Thus all armchair (n=m) nanotubes are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are semiconducting. In theory, metallic nanotubes can have an electrical current density more than 1,000 times greater than metals such as silver and copper.

  13. 三、Compounds • 1. [ - 4 ] O.S. • 水解性(或与水反应) • Al4C3 + 12H2O = 4Al(OH)3 + 3CH4↑ • CaC2 + 2H2O = Ca(OH)2 + HCCH • 2. [ + 4 ] O.S • (1) CHal4 • a. 制备 CS2 + 3Cl2 = CCl4 + S2Cl2 • b. 性质 水解性

  14. CHal4 + 2H2O = CO2 + 4HHal • 从热力学上看是可行的，它们之所以不能水解是由 • 于在通常条件下缺乏动力学因素，碳的配位数已饱 • 和，不能与水分子结合 • 从CF4 CI4随着键长的增大,键的强度减弱,稳定 • 性减弱,活泼性增强

  15. (2) COHal2（卤氧化碳或碳酰卤）: • 所有的COHal2比CHal4的化学性质活泼,特别是它 • 们易水解: • COCl2 + H2O = CO2 + 2HCl • 它们都有极性,都是平面三角形。 • COCl2 (光气) 是剧毒的 • 光气的制备: • CO + Cl2 =COCl2

  16. (3) CS2 • a. Preparation • (i) C+ 2S = CS2 (900C) • (ii) 4S + CH4 = CS2 + 2H2S (600C, Al2O3或硅胶) • b. Properties • CS2易挥发,易燃的无色的有机溶剂 • 明显水解 CS2+ 2H2O = CO2 + 2H2S • 与碱性硫化物反应 Na2S + CS2 = Na2CS3

  17. (4) CO32- CS32- CN22- • a. structure • b. 性质 • (i) 碳酸盐: 正盐中除碱金属(不包括Li+)，铵及Tl+盐 • 外都难溶于水,许多金属的酸式盐的溶解度大于正盐,但 • SNaHCO3 < SNa2CO3 • 解释:这是由于在NaHCO3溶液中HCO3-以氢键相 • 连成二聚或多聚链状离子,降低了它们的溶解度 • 热稳定性： H2CO3 < MHCO3 < M2CO3

  18. H+ • (ii) 硫代碳酸盐 • K2S + CS2 = K2CS3 = H2CS3 • H2CS3是高折射率油状物，易分解成H2S和CS2 • H2CS3的水溶液为弱酸，在水中缓慢分解 • H2CS3 + 3H2O = H2CO3 + 3H2S • (iii) 氨基腈化物 (Cyanamide) (CN22-)（氮代碳酸盐） • H2CN2 (Hydrogen dinitride carbonate )是无色晶 • 体，易溶于水，alcohol和ether，显示弱酸性，在有 • 机溶剂中可能存在互变异构平衡

  19. H2CN2在水中缓慢分解: • H2CN2 + 3H2O = H2CO3 + 2NH3 • 3. [ +2 ] O.S. • HCOOH = CO + H2O (浓硫酸，加热) • CO结构式： 使μ减小 • CO + PdCl2 + H2O = Pd + CO2 + 2HCl • Cu(NH3)2+可以吸收CO，所以CO比N2活泼 常温 CO2 v.s. CO

  20. §14-2 Silicon and its compounds • 一、General properties: • 1. 由于Si的原子半径大，电离能低，电子亲合能和 • 极化率高，因此Si在化学性质上与碳有许多不同之处，例如Si和Si之间基本上不形成pπ－pπ键，换言之，Si的sp或sp2杂化不稳定。 • 2. 由于Si原子的价轨道存在3d空轨道,所以Si的最大 • 配位数可以达到6，可以形成d—p键，例如N(SiH3)3中N原子采取sp2杂化，分子为平面三角形。这是由于N原子上的孤对电子对占有Si原子的3d空轨道，形成d－pπ键所致。显然N(CH3)3与N(SiH3)3的碱性也不同，前者的Lewis碱性大于后者。 • 3. Si在自然界中占第二位，仅次于氧

  21. 二、The simple substance • 1. Properties • (1) 在通常情况下，硅非常惰性 ，但加热时与许多非金属单质 • 化合，还能与某些金属反应 • 2Mg + Si = Mg2Si • (2) 硅遇到氧化性的酸发生钝化性,它可溶于HF—HNO3的混合 • 酸中 3Si + 4HNO3 + 18HF = 3H2SiF6 + 4NO + 8H2O • (3) 硅溶于碱并放出H2: Si + 2KOH + H2O = K2SiO3 + 2H2↑ • (4) 硅在高温下与水蒸气反应: Si + 3H2O = H2SiO3 + 2H2↑

  22. Silicon nitride (Si3N4) is a hard, solid substance, that can be obtained by direct reaction between silicon and nitrogen at high temperatures. Silicon nitride is the main component in silicon nitride ceramics, which have relatively good shock resistance compared to other ceramics. Rollers made of silicon nitride ceramic are sometimes used in high-end skateboard bearings, due to the material's shock and heat-resistant characteristics. It is also used as an ignition source for domestic gas appliances, hot surface ignition. In microelectronics, silicon nitride is usually formed using chemical vapor deposition (CVD) method, or one of its variants, such as plasma-enhanced chemical vapor deposition (PECVD). It is usually used either as an insulator layer to electrically isolate different structures or as an etch mask in bulk micromachining. As a passivation layer for microchips, it is superior to silicon dioxide, as it is a significantly better diffusion barrier against water molecules and sodium ions, two major sources of corrosion and instability in microelectronics. It is also used as a dielectric between polysilicon layers in capacitors in analog chips. Bulk, monolithic silicon nitride is used as a material for cutting tools, due to its hardness, thermal stability, and resistance to wear. It is especially recommended for high speed machining of cast iron. For machining of steel, it is usually coated by titanium nitride (usually by CVD) for increased chemical resistance.

  23. Lightning Arresters In telegraphy and telephony a lightning arrester is placed where wires enter a structure, preventing damage to electronic instruments within and ensuring the safety of individuals near them. Lightning arresters, also called surge protectors,are devices which are connected between each electrical conductor in a power and communications systems and the earth. These provide a short circuit to the ground that is interrupted by a non-conductor over which lightning jumps. Its purpose is to limit the rise in voltage when a communications or power line is struck by lightning. The non-conducting material may consist of a semi-conducting material like silicon carbide or zinc oxide, or a spark gap. Primitive varieties of such spark gaps are simply open to the air, but more modern varieties are filled with dry gas and provided with a small amount of radioactive material to encourage the gas to ionize when the voltage across the gap reaches a specified level. Other designs of lightning arresters use a glow-discharge tube (essentially like a neon glow lamp) connected between the protected conductor and ground, or any one of a myriad of voltage-activated solid-state switches called varistors or MOV's. Lightning arresters built for substation use are impressive devices, consisting of a porcelain tube several feet in length and several inches in diameter, filled with disks of zinc oxide. A safety port is supplied on the side of the device to vent the occasional internal explosion without shattering the porcelain cylinder.

  24. 2. preparation: • (1) SiCl4 + 2Zn = Si + 2ZnCl2 • (2) SiO2和C混合，在电炉中加热: • SiO2 + 2C = Si + 2CO↑ • (3) SiO2 + CaC2 = Si + Ca + 2CO • (4) 硅烷的分解: SiH4 = Si + 2H2 • 用作半导体用的超纯硅，需用区域熔融的方法提纯 >99.999999%

  25. 三、Compounds • 1. 硅的金属化合物与硅合金 • (1) IA、 IIA族硅化物: Ca2Si , CaSi , CaSi2 • 不稳定，与水反应 • (2) 副族元素硅化物: • Mo3Si , Mo5Si3 , MoSi , MoSi2 （2050℃） • 高熔沸点，不溶于HF和王水，仅溶于HF— • HNO3混合液或者在碱液中 • WSi2（2165℃），Ti5Si3（2120℃），V5Si3（2150℃），f区元素的硅化物在反应堆中吸收中子。

  26. 2. [ +4 ] O.S. SiHal4，SiO2，Si3N4，SiC和SiH4 • (1) Structure: • 正四面体结构单元: SiO4 , SiS4 , SiN4 ,SiC4 • (2) properties: • a. 与碱反应: • SiO2 + Ca(OH)2 = CaSiO3 + H2O • SiH4 + 2KOH + H2O = K2SiO3 + 4H2 • CaS + SiS2 = CaSiS3

  27. b. Hydrolysis • (i) SiCl4 + 4H2O = H4SiO4 + 4HCl • SiS2 + 4H2O = H4SiO4 + 2H2S • (ii) SiF4 + 3H2O = H2SiO3 + 4HF • 4HF + 2SiF4 = 2H2SiF6 • 即：3SiF4 + 3H2O = H2SiO3 + 2H2SiF6 • (3) SiHal4制备 • a. CaF2 + H2SO4 = CaSO4 + 2HF • SiO2 + 4HF = SiF4 + 2H2O • b. SiO2 + 2C + 2Cl2 = SiCl4 + 2CO

  28. H2O • (4) 硅烷 SinH(2n+2) n可高达15 • a. preparation: • Mg2Si + 2H2SO4 = SiH4 + 2MgSO4 • Mg2Si + 4NH4Br = SiH4 +2MgBr2 + 4NH3 • SiCl4(l) + LiAlH4(s)= SiH4(g) + LiCl(s) + AlCl3(s) • b. properties • (i) reduction: • SiH4 + 2KMnO4 = 2MnO2↓+ K2SiO3 + H2O + H2↑ • 可以用KMnO4来鉴别在纯水中硅烷 • (ii) hydrolysis: SiH4在纯水和微酸性溶液中不水解，但在 • 微量碱作催化剂时，迅速水解生成硅酸与氢气 NH3 Silicone rubber

  29. (5) 硅酸(Silicic acid)及硅酸盐 • a. 可溶性酸盐与H+ , CO2 , NH4+反应得到H2SiO3 • b. 硅酸盐结构 • (i) 每个[SiO4]四面体Si:O=1:4,化学式为SiO44- • (ii) 两个[SiO4]以角氧相连，Si和O的原子数之比是1:3.5，化 • 学式为Si2O72- • (iii) [SiO4]以两个角氧分别和其它[SiO4]两个角氧相连成环状或长链状结构，Si:O=1:3 • (iv) [SiO4]以角氧构造成双链，Si︰O = 4︰11， • (v) [SiO4]分别以三角氧和其它三个[SiO4]相连成层状结构 • (vi) [SiO4]分别以四个氧和其他四个相连成立体结构，SiO2

  30. Si:O=1:3

  31. §14-3 Germanium Subgroup • 一、General properties • +4氧化态稳 Ge Sn Pb +2氧化态稳 • 　 定性增大 定性增大 • 自然界中存在tinstone 锡石(SnO2)， galena (方 • 铅矿) (PbS) • 铅存在于Uranium 和Thorium矿中，这是由于铅是U和Th放射性衰变的产物 Pb可防alpha, gamma和X-ray但对beta和neutron效果差

  32. 13.6C 161 C • 二、The simple substances • 1. Allotropes: • 灰锡(α锡) 白锡(β锡) 脆锡 • 2. Properties: • (1) Tin是两性金属 • Sn + 2HCl = SnCl2 + H2↑ • Sn + 2OH- + 2H2O = Sn(OH)42- + H2↑ (加热) • (2) Ge只有在H2O2（氧化剂）存在下，才溶于碱 • Ge + 2KOH + 2H2O2 = K2[ Ge(OH)6 ]

  33. Pb也能与碱反应： • Pb + 2H2O + 2KOH = K2[ Pb(OH) 4 ] + H2↑ • (2) 与氧化性酸反应: • a. Pb与任何浓度的硝酸反应都得到Pb(NO3)2 • b. Sn与浓HNO3反应得到Sn(IV)，与稀HNO3反应得 • 到Sn(II) • 3Sn + 8HNO3 (稀)= 3Sn(NO3)2 + 2NO + 4H2O • Sn + HNO3 (浓) = H2SnO3 + NO2 + H2O

  34. 三、Compounds • 1. 卤化物 EHal4 EHal2 • (1) SnCl2 • a. 水解性 SnCl2 + H2O = Sn(OH)Cl↓ + H+ + Cl- • 在配制SnCl2必须防止氧化和水解 • 用盐酸酸化蒸馏水，并在SnCl2中加入Sn粒。 • b. 还原性 • SnCl2 +2HgCl2 = SnCl4 + Hg2Cl2 • Hg2Cl2 + SnCl2 = SnCl4 + 2Hg↓

  35. (2) GeCl4 , SnCl4也强烈水解 • GeCl4 + 2H2O = GeO2↓ + 4HCl • SnCl4 + 4H2O = Sn(OH)4 + 4HCl • 在盐酸中：SnCl4 + 2HCl = H2SnCl6 • (3) PbCl2在冷水中溶解度小，但在热水中溶解度 • 大，在盐酸中溶解度增大 • 因为PbCl2 + 2Cl- = PbCl42- • (4) PbCl4在低温下稳定，在常温下即分解 • PbCl4 = PbCl2 + Cl2

  36. 2. 硫化物 • (1) SnS: H2S + Sn2+ = SnS↓(暗棕色)+ 2H+ • SnS不溶于Na2S溶液中，但可溶液于中等浓度的 • HCl和碱金属的多硫化物溶液中 • SnS + 4Cl- + 2H= = SnCl42- + H2S↑ • (2) SnS2 • Sn4+ + 2H2S = SnS2↓+ 4H+ • SnS2 + S2- = SnS32- 2

  37. (3) PbS: Pb2+ + S2- = PbS↓(黑色) • PbS可溶于浓HCl和稀HNO3、H2O2，不溶于Na2S • 和无氧化性的稀酸 • PbS + 4HCl(浓) = H2S↑ + H2PbCl4 • 3PbS + 2NO3- + 8H+ = • 3Pb2+ + 3S↓ + 2NO↑ + 4H2O • 由于Pb(IV)有极强的氧化性，所以PbS2不存在

  38. 3. 一些铅的化合物 • (1) 氧化物 • PbO(黄色) 密陀僧（massicot） Pb2O3(黄色) (PbO·PbO2) Pb3O4(红色) (2PbO·PbO2) 铅丹 PbO2(黑色) • Pb2O3 , Pb3O4 , PbO2都具有强氧化性 • 5PbO2 + 2Mn2+ + 4H+ = 5Pb2+ + 2MnO4- + 2H2O • PbO2 + 4HCl = PbCl2 + Cl2↑+ 2H2O

  39. (2) Pb(NO3)2 • 易水解：Pb2+ + NO3-+ H2O = Pb(OH)NO3↓+H+ • 易分解：2Pb(NO3)2 = 2PbO + 4NO2 + 2H2O • (3) Pb(CH3COO)2 • 易溶于水，难离解，毒性大 • Pb(Ac)2 + Cl2 + 4KOH = PbO2 + 2KCl + 2KAc + 2H2O • (4) PbSO4 • 可溶于浓H2SO4中,也可溶于NH4Ac或NaAc溶液中

  40. H+ OH- • (5) PbCrO4(黄色) PbCr2O7(可溶) • (6) 铅的有机化合物 • Na4Pb (铅钠合金) + 4C2H5Cl = Pb(C2H5)4 + 4NaCl • 四乙基铅是汽油抗震剂，其∆HfΘ=217.6KJ·mol-1 ， • 但在常温下尚能稳定存在。 • 由于用Pb(C2H5)4作为汽油抗震剂，汽油燃烧后的废 • 气中含有铅的化合物，污染环境

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