Group 4A (14) CARBON FAMILY (ns 2 np 2 )

Group 4A (14) CARBON FAMILY (ns 2 np 2 )

General electron configuration: [ ] ns 2 (n 1)d 10 np 2 ns 2 np 2 nd 0 Oxidation states: 4, 0, +2, +4 Stable oxidation states: С, Si, Ge, Sn: +IV Pb: +II

Bonding in Group 4A(14) Compounds Carbon forms predominantly covalent bonds, but the larger members of the group form bonds with increasing ionic character. Elements of this group also exhibit multiple oxidation states. Lower oxidation states become more prominent down the group. Pb and Sn show more metallic character in their lower oxidation states. SnCl 2 and PbCl 2 are white, crystalline solids with high melting points. SnCl 4 is a volatile, benzene-soluble liquid.

Bond Type and the Melting Process in Group 4A

Allotropes Allotropes are different crystalline or molecular forms of the same element. One allotrope of a particular element is usually more stable than another at a particular temperature and pressure. Carbon has several allotropes, including graphite, diamond, and fullerenes. Tin exhibits two allotropes; white β-tin and gray α-tin. C

Diamond and graphite White tin Gray tin diamond Graphite

Important ores of Carbon group elements 2. Si 25,80% 13. C 0,087% 31. Sn 0,0035% 35. Pb 0,0018% 46. Ge 6 10 4 % Silicon: Quartz, Jasper, agate, opal, silicates, alumosilicates Quartz Amethyst Opal Agate Kaolinite

Carbon: graphite, diamond, coal, oil, gas, organic compounds, carbonates Graphite Calcite Gas Diamond Coal

Ge, Sn, Pb Cassiterite SnO 2 Galena PbS Argyrodite (Ag 8I Ge IV )S 6 Germanite (Fe II Cu 6I Ge 2 )S 8

Important reactions of Carbon group elements At room temperature. С, Si, Ge + H 2 O С, Si, Ge + H 3 O + Sn, Pb + H 2 O Sn + H 3 O + Sn 2+ + H 2 Pb + H 3 O + Pb 2+ + H 2

Important reactions of Carbon group elements С + KOH Si + 4NaOH = Na 4 SiO 4 + 2H 2 Ge + 2KOH + 2H 2 O 2 = K 2 [Ge(OH) 6 ] Sn + NaOH + 2H 2 O = Na[Sn(OH) 3 ] + H 2

Important reactions of Carbon group elements 1. The elements are oxidized by halogens: M + 2 Hal 2 MHal 4 (M = C, Si, Ge) The +2 halides are more stable for tin and lead, SnHal 2 and PbHal 2. 2. The elements are oxidized by O 2 : M (s) + O 2(g) MO 2(-) (M = C, Si, Ge, Sn) Pb forms the +2 oxide, PbO. Oxides become more basic down the group. The reaction of CO 2 and water provides the weak acidity of natural unpolluted waters: CO 2(g) + H 2 O (l) [H 2 CO 3 ] H + (aq) + HCO 3 - (aq) carbonic acid

EHal 2, EHal 4 (Sn, Pb) +Hal 2 EO, EO 2 (Sn, +O Pb) 2 OH E IVA +S ES, ES 2 SiO 4 4 [E(OH) 3 ] + H 2 (Sn, Pb) HNO 3 (c) HNO 3 (d) H 3 O + E 2+ + H 2 (Sn, Pb) CO 2, Pb 2+, SnO 2 nh 2 O Sn 2+, Pb 2+

Important compounds of Carbon group elements

Acidic oxides Reducing properties Amphoteric Do not form salts OXIDES of IVА group +IV +II CO 2 (g) stable. SiO 2 (s) stable GeO 2 (s) stable SnO 2 (s) stable PbO 2 (s) strong oxidizing agent CO SiO GeO SnO PbO stable.

Hydrides of elements IVА-group СH 4 SiH 4 GeH 4 SnH 4 PbH 4 unstable.

Carbon compounds in different oxidation states +IV +II CO 2, CO 32, H 2 CO 3, Na 2 CO 3, CS 2, CF 4, CCl 2 O, C(NH 2 ) 2 O CO, HCN, C 2 F 4 0 C IV СH 4, Be 2 C, Al 4 C 3, SiC

Graphite is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Т. melt. 3800 С, т. boil. 4000 С, density 2,27 г/см 3, elect. condact., stable. Strong reducing agent (reacts with hydrogen, oxygen, fluorine, sulfur, metals). Graphite has a layered, planar structure.

Diamond diamond has the highest hardness and thermal conductivity of any bulk material. is a metastable allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice.. Diamond is less stable than graphite.

Carbyne and fullerene Carbyne: is an allotrope of carbon that has the chemical structure ( C C )n as a repeating chain, with alternating single and triple bonds., uncolored, semiconductor; density 3,27 g/cm 3. Fullerene: С 60 и С 70 is a molecule of carbon in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes are also called Buckminsterfullerene (buckyballs), and they resemble the balls used in football (soccer)., dark powder, semiconductor, mp. 500-600 C, density 1,7 g/cm 3 (С 60 ). Fullerene С 60 Fullerene С 70

Carbides Calcium carbide Salts-like (CaC 2, Al 4 C 3 ) CaC 2 + 2H 2 O = Covalent (SiC) Metal-like(Fe 3 C, CW) Al 4 C 3 + 12H 2 O = = Ca(OH) 2 + C 2 H 2 = 4Al(OH) 3 + 3CH 4 Silicon carbide Alloy on base of CW Silicon carbide, SiC. Known as carborundum, a major industrial abrasive and a highly refractory ceramic for tough, high-temperature uses. Can be doped to form a hightemperature semiconductor.

Hydrogen compounds. Methane CH 4 sp 3 СН 4 Used as a fuel and in the production of many organic compounds. Major component of natural gas. Formed by anaerobic decomposition of plants (swamp gas) and by microbes in termites and certain mammals. No smell, no color. Preparation in lab: CH 3 COONa + NaOH (+t) = = Na 2 CO 3 + CH 4 Burning: CH 4 + O 2 = С + 2H 2 O CH 4 + 2O 2 (excess) = СO 2 + 2H 2 O

Carbon monoxide CO Used as a gaseous fuel as a precursor for onecarbon organic compounds, and as a reactant in the purification of nickel. Formed in internal combustion engines and released as a toxic air pollutant. Uncolored gas, without smell, lighter then air, slightly soluble in water, b.p. 191,5 С, toxic. Reducing properties: 4CO + Fe 3 O 4 = 3Fe + 4CO 2 (pyrometallurgy)

Carbon monoxide CO Dative properties: CO forms very stable complexes with d metals [Fe(CO) 5 ]. Fe : C ::: O Identification: PdCl 2 + CO + H 2 O = Pd + CO 2 + 2HCl I 2 O 5 + 5CO = I 2 + 5CO 2

Carbon dioxide CO 2 ( acidic oxide) O,, С O «Dry ice» Uncolored, no smell, slightly soluble in water (at RT in 1 L of water 1,7 L of CO 2 ). Solid state - («dry ice») The final oxidation product of all C - based fuels; its increase in the atmosphere is leading to global warming. Used industrially as a refrigerant gas, blanketing gas in fire extinguishers, and effervescent gas in beverages. Combined with NH 3 to form urea for fertilizers and plastics manufacture.

Carbonic acid H 2 CO 3 In aqua's solution: CO 2 (г) + H 2 O CO 2. H 2 O H 2 CO 3 H 2 CO 3 weak bibasic acid: H 2 CO 3 + H 2 O HCO 3 + H 3 O + ; K K = 4,27 10 7 HCO 3 + H 2 O CO 3 2 + H 3 O + ; K K = 4,68 10 11 salts carbonates and bicarbonates M 2 CO 3 и MHCO 3 hydrolyses (рн > 7). Thermal decomposition of carbonates: 2NaHCO 3 = Na 2 CO 3 + CO 2 + H 2 O

Cyanhydric acid Cyanhydric acid HCN uncolored liquid. Very weak acid: HCN + H 2 O CN + H 3 O + ; K K = 4,93 10 10 Salts are very toxic. Fe : C:::N

Thiocyanhydric acid Thiocyanhydric acid HNCS is not toxic. Strong acid H.. N C S: sp 2 sp

Carbon in Organic Chemistry The large number and wide variety of organic compounds is due to the ability of C to bond to itself, and to form multiple bonds. Catenation is the process whereby carbon bonds to itself to form stable chains, branches, and rings. Since C is small, the C-C bond is short enough to allow effective side-to-side overlap of p orbitals. C readily forms double and triple bonds.

Three of the several million known organic compounds of carbon. Lysine, one of 20 amino acids that occur in proteins

Highlights of Silicon Chemistry Silicon bonds to oxygen to form repeating Si Oi units, which are found in silicates and silicones. The silicate building unit is the orthosilicate grouping, SiO 4, which has a tetrahedral arrangement. Silicate minerals are the dominant form of matter in the nonliving world. They include clay, sand, and semiprecious stones. Silicone polymers are synthetic substances consisting of alternating Si and O atoms. They are used in a wide variety of applications.

Silicon Reactivity with acids 3Si + 4HNO 3 + 18HF = 3H 2 [SiF 6 ] + 4NO + 8H 2 O Si + 4NaOH = Na 4 SiO 4 + 2H 2 Preparation SiO 2 + 2Mg = 2MgO + Si SiCl 4 + 2H 2 = Si + 4HCl

Figure 14.14 Structures of the silicate anions in some minerals.

Hydrogen compounds Si n H 2n+2 (silanes) Monosilane SiH 4 : SiH 4 + 2O 2 = SiO 2 + 2H 2 O Preparation: SiO 2 + 4Mg = Mg 2 Si + 2MgO (magnesium silicide) Mg 2 Si + 4H 2 O = 2Mg(OH) 2 + SiH 4 Mg 2 Si + 4H 3 O + = 2Mg 2+ + 4H 2 O + SiH 4

Oxygen compounds of silicon SiO 2 GeO 2 + H 2 O SiO 2 GeO 2 + H 3 O + SiO 2 + 4NaOH(р) = Na 4 SiO 4 + 2H 2 O (sodium orto silicate soluble glass silicate glue) GeO 2 + 2NaOH(т) = Na 2 GeO 3 + H 2 O Silicon dioxide, SiO 2. Occurs in many amorphous (glassy) and crystalline forms, quartz being the most common. Used to make glass and as an inert chromatography support material.

Quartz is a three-dimensional framework silicate.