CHM 104 Chemistry of Group IV Elements 2023-24 PDF

24/05/2024 INTRODUCTION TO INORGANIC CHEMISTRY (2UNITS) CHM 104/ Chemistry Chemistry of Group IVA Elements (Carbon Group) 1 2...

24/05/2024 INTRODUCTION TO INORGANIC CHEMISTRY (2UNITS) CHM 104/ Chemistry Chemistry of Group IVA Elements (Carbon Group) 1 2 1  24/05/2024 Occurrence and Uses of Group IVA Elements: Carbon Carbon occurs as crystalline allotropes (diamond and graphite) and molecular allotrope (fullerenes). Diamond occurs naturally in igneous rocks which can be found in South Africa. Graphite occurs naturally in many areas eg. Republic of Korea, Austria, China, Mexico, Madagascar, Germany, Sri Lanka, and Russia. Fullerenes occur naturally in a number of deposits in Australia, New Zealand and North America. Carbon also exists as carbon (IV) oxide (CO2) at 0.04% of the earth’s atmosphere 3 What is Allotropy? Allotropy, the existence of a chemical element in two or more forms, which may differ in the arrangement of atoms in crystalline solids or in the occurrence of molecules that contain different numbers of atoms. (https://www.britannica.com/science/allotropy, 2019) 4 2  24/05/2024 Allotropes of Carbon Eight allotropes of carbon: a: Diamond, b: Graphite, c: Lonsdaleite, d: C60 (Buckminsterfullerene or buckyball), e: C540, f: C70, g: Amorphous carbon, and h: single- walled carbon nanotube or buckytube. Courtesy :Wikipedia 5 Allotropes of Carbon The crystal structure of diamond. 6 3  24/05/2024 Allotropes of Carbon Natural Graphite A view of the planes of atoms in the structure of graphite. 7 Allotropes of Carbon Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in structure. 8 4  24/05/2024 Allotropes of Carbon Characteristics Diamond Graphite Density 3.5gcm-3 2.3gcm-3-less dense than diamond because its structure is less compact. Structure A three dimensional array of carbon A two dimensional array of carbon atoms, atoms, each atom surrounded each atom surrounded by three other carbons tetrahedrally by four other carbons. in the same plane and the bonding is Each diamond crystal is a giant covalent. The sheet of carbon atoms are molecule containing very strong arranged in regular hexagon and are held by bonds. The structure is highly rigid. weak van der Waal’s forces. Hardness Hardest naturally occurring Very soft and slippery because the weak substance forces holding the individual sheets together are easily broken, the sheets are easily moved relative to one another. Electrical Does not conduct electricity Graphite conducts electricity. Since each carbon atoms is surrounded by three other carbons, thus alternate single and double bonds must be present to complete the octet of each carbon atom. The presence of the double bonds means that mobile electrons are present and these can readily be transferred from one hexagon to another by the application of an electric field. 9 Allotropes of Carbon The structure of C60 Fullerenes Aka buckminsterfullerene Sir Harold W. Kroto with models (Courtesy :Encyclopædia Britannica) of fullerenes, 1996. 10 5  24/05/2024 Allotropes of Carbon Characteristics Fullerenes also known as buckminsterfullerene Discovery First discovered in 1985 by Sir Harold W. Kroto of the United Kingdom and by Richard E. Smalley and Robert F. Curl, Jr., of the United States. Structure Cagelike molecules composed of 60 carbon atoms (C60) joined together by single and double bonds to form a hollow sphere with 12 pentagonal and 20 hexagonal faces Properties It readily accepts and donates electrons The molecule readily adds atoms of hydrogen and of the halogen elements which can be replaced by other groups, such as phenyl-C6H5, thus opening useful routes to a wide range of novel fullerene derivatives. Endohedral species of the Fullerenes also exists, in which a metal atom is physically trapped inside a fullerene cage. The resulting compounds (assigned the formulas M@C60) have been extensively studied. These derivatives exhibit advanced materials behaviour 11 Applications of Allotropes of Carbon Diamond is used as gemstones, cutting tools, abrasives etc Graphite is used as a lubricant. It is exploited commercially for its inertness, high thermal stability, electrical and thermal conductivities. A single layer of graphite is called graphene and has extraordinary electrical, thermal, and physical properties. Fullerenes are applied as nanotubes in materials science.[owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes find applications as additives to various structural materials, also for medical uses.]. Has potentials for great uses. 12 6  24/05/2024 The main parts of a pencil are the graphite rods (Courtesy :Encyclopædia Britannica) 13 Spinning Carbon Nanotube (Courtesy :Wikipedia) 14 7  24/05/2024 Occurrence and Uses of Group IVA Elements: Silicon Elemental Si does not exist naturally but constitutes 25.7% of the earth’s crust in the form of sand, quartz etc Uses Silica sand Si is utilized in steel industries, electronic and semiconductor industries. It is also used as the main component of glass in the form of silica(SiO2) Quartz Silicon sand 15 Occurrence and Uses of Group IVA Elements: Germanium Germanium Ge constitutes 1.8ppm of the earth’s crust Uses Used as polymerization catalysts for the production of polyethylene; fibre optics, optical devices (GeO2), as semiconductors in electronic and solar electrical industries. Germanium semi conductor 16 8  24/05/2024 Occurrence and Uses of Group IVA Elements: Tin Cassiterite Sn occurs naturally as the ore cassiterite (SnO2) Uses Used for tin plating for example in steel cans to improve corrosion resistance. Also used as alloys eg bronze. 17 Occurrence and Uses of Group IVA Elements: Lead Pb occurs naturall as the ore: galena(PbS), anglesite(PbSO4) and cerussite (PbCO3) Uses Used in industry plant; as Lead acid batteries. Lead oxides are used in the making of lead crystal glass Lead(IV) oxide as an oxidizing agent in the production of dyestuffs, chemicals etc 18 9  24/05/2024 Galena (aka Lead Glance) https://geology.com/minerals/galena.shtml 19 Occurrence and Uses of Group IVA Elements: Flerovium 1. It is a superheavy chemical synthetic element. 2. It was discovered by Yuri Oganessian and Vladimir Utyonkov in 1998 3. It is named after the Russian physicist Georgy Flerov, the founder of the Joint Institute for Nuclear Research (JINR) where the element was discovered 4. Discovered by the bombarding of plutonium with calcium. The reaction produced a single atom of flerovium- 289, the most stable of its isotopes with a half-life of 2.1 seconds 5. At present, it is only used in research. 6. Flerovium can be formed in nuclear reactors 𝑃𝑢 + 𝐶𝑎 → 𝐹𝑙 + 3 𝑛 20 10  24/05/2024 SOME PHYSICAL AND CHEMICAL PARAMETERS OF GROUP IV ELEMENTS Germanium Element Carbon C Silicon Si Tin Sn Lead Pb Ge Atomic No 6 14 32 50 82 Electronic 1s22s22p2 [Ne]3s23p2 [Ar]4s24p2 [Kr]4d105s25p2 [Xe]4f145d106s26p2 Configuration Atomic radii 0.077 0.117 0.122 0.140 0.154 (nm) Melting pointºC 3730d 1410 937 232 327 Boiling pointºC 4830d 2360 2830 2270 1744 Farily Conductivity goodgr Semi-cond Semi-cond Good Good Non-cond.d First ionization 1086 787 760 707 715 energy/kJ mol-1 Giant Giant molecule Type of Giant molecule similar to Giant metallic Giant metallic Structure molecule similar to diamond diamond gr-graphite d-diamond 21 Some physical properties of Group IV elements Metallic Properties: Carbon and silicon are non- metallic. Germanium has both metallic and non- metallic properties (metalloid). Tin and lead are definitely metallic. Stucture: The structure changes from giant molecular lattices in carbon and silicon to giant metallic structure in tin and lead. 22 11  24/05/2024 Valency They exhibit a valency of 2 and 4 carbon and silicon compounds, the 4-valent states are very stable relative to 2-valent state. The 2-valent state is rare and easily oxidised to 4-valent state. CO is reacts very exothermically to form CO2. Germanium forms oxides in both 2-valent and 4-valent state. However, GeO2 is rather more stable than GeO. GeO2 does not act as an oxidising agent and GeO is readily converted to GeO2. 23 Valency- The compounds of Sn and Pb are often predominantly ionic. In tin compounds, the 4-valent states are slightly more stable than the 2-valent state Sn 2 (aq)  Hg 2 (aq) Sn 4 (aq)  Hg(l) Sn 2 (aq)  I 2 (aq) Sn 4 (aq)  2I  (aq) 24 12  24/05/2024 Valency- For lead compounds, 2-valent state is the most predominant. PbO2 is a strong oxidising agent, while PbO is relatively stable. PbO 2 (s)  4HCl(aq) PbCl 2 (aq)  Cl 2  2H 2 O(l) 2PbO 2 (s)  4H 2S(g) 2PbS(s)  S2 g   4H 2 O(l) Inert pair effect Ge, Sn and Pb form 2-valent compounds in which the two s electrons are inert (inert pair effect- because, as each of the two electrons is removed form p orbital, the remainder in the s-orbital are held more strongly by the increased positive charge- in the s orbital) and the stability increases from Ge to Pb. 25 Chemical properties: Silicon At high temperatures, Si combines with Silicon liberates O2, F2, Cl2, Br2, H2 from I2, S8, N2, P4, C aqueous alkali and B to give but is insoluble binary in acids other compounds. than a mixture of concentrated Si HNO3 and HF. Silicon is 𝑆𝑖 + [𝑂𝐻] → 𝑆𝑖𝑂 + 2𝐻 much more reactive than carbon 26 13  24/05/2024 Chemical properties:Germanium Germanium is more electropositive than Silicon. Reacts with HCl to give Reacts with GeCl4. Conc HNO3 to form Ge GeO2. Reacts with H2S Does not to give react with GeS2. aqueous alkali 27 Chemical properties: Tin Reacts with dilute HNO3 to form Sn(NO3)2 and NH4NO3. Lttle affected by Reacts readily dilute HCl or with halogens H2SO4 but when to give SnX4. Sn concentrated will yield SnCl2 and SnSO4/SO2 respectively Reacts with O2 and sulphur at high temp. to give SnO2 and SnS2 respectively.. 28 14  24/05/2024 Chemical properties: Lead When finely divided, Pb is pyrophoric, but Pb reacts very bulk pieces are slowly with passivated by dilute mineral coatings. acids Pb Reacts with concentrated HNO3 to give Slowly Pb(NO3)2 and evolves H2 oxides of from hot nitrogen concentrated HCl {A pyrophoric material is spontaneously 29 inflammable} Some Simple compounds of Group IV elements Hydrides--tetravalent hydrides XH4 CATENATION is a unique ability of this group in which they forms stable compounds containing long chains and rings of atoms. Hydrocarbons: eg alkanes, alkenes and alkynes. The ability of carbon to catenate results from the fact that the C-C bond is almost as strong as the C-O bond [C-C=346 kJmol-1, C-O=360 kJmol-1]. Silanes: Si-Si bond is much weaker than Si-O bond [Si- Si=226kJmol-1, Si-O=464kJmol-1], therefore catenated compounds of silicon are energetically unstable with respect to SiO2 and does not occur naturally. SiH4 is spontaneously flammable in air. Germane, Stannane And Plumbane: eg GeH4, SnH4 and PbH4 30 15  24/05/2024 Some Simple compounds of Group IV elements Halides-----All the elements in this group react directly with halogens to form the tetrahalides (CCl4, SiCl4), except lead which forms the dihalides (PbCl2). Oxides----All members of the group except lead reacts with oxygen on heating to form the dioxide(CO2, SiO2). Lead forms the monoxide, PbO. Carbides, silicides: These are solid state binary compounds that some members of this group form with metals. Examples: metal carbides are CaC2, K2C2; metal silicides(Mg2Si, Ca2Si.) Ge, Sn and Pb do not form solid state binary compounds with metals 31 Carbon dioxide:Greenhouse effect Diagram showing light energy (white arrows) emitted by the sun, warming the earth's surface which then emits the energy as heat (orange arrows), which warms the atmosphere and is then re-emitted as heat by three of the greenhouse gas molecules (water, carbon dioxide, and methane) (Wikipedia,2019) 32 16  24/05/2024 Carbon dioxide:Greenhouse effect Google image, 2019 33 Carbon dioxide: Dry Ice Dry Ice is the solid form of carbon dioxide Dry ice sublimates at 194.65 K at Earth atmospheric pressures Dry ice is colourless, non- flammable, with a sour zesty odor, and can lower the pH of a solution when dissolved in water, forming carbonic acid (H2CO3). 34 17  24/05/2024 Dry ice pellet subliming in water, releasing thick white fog. 35 Wikipedia, 2019 Charcoal a form of Carbon Charcoal This is an impure form of graphitic carbon, It is obtained as a residue when carbonaceous material is partially burned, or heated with limited access of air. Coke, carbon black, and soot may be regarded as forms of charcoal Most important use has been as a metallurgical fuel Activated charcoal is a black, odorless, flavorless powder that has been used since ancient times to treat various ailments. Used as an anti-poison remedy, reducing gas and flatulence, lower cholesterol levels and improved kidney function. Also used in skin care Britannica, The Editors of Encyclopaedia. "charcoal". Encyclopedia Britannica, 26 Sep. 36 2022, https://www.britannica.com/science/charcoal. Accessed 3 November 2022. 18  24/05/2024 Silicone Polymers Elemental silicon is usually prepared by the high- temperature reduction of silica (sand) with coke. Excess SiO2 prevents the formation of silicon carbide. Elemental silicon is used to make silicone polymers. 37 38 19  24/05/2024 Asbestos “Asbestos” refers to a group of impure magnesium silicate minerals. Asbestos is a fibrous material. When inhaled, these fibers are highly toxic and carcinogenic. 39 The ability of the fibres to be woven along with their heat resistance and high tensile strength led to widespread applications of asbestos in fire- proofing materials, brake linings, prefabricated boards for construction, roofing tiles and insulation. 40 20  24/05/2024 Silicone Polymers Elemental silicon is usually prepared by the high- temperature reduction of silica (sand) with coke. Excess SiO2 prevents the formation of silicon carbide. Elemental silicon is used to make silicone polymers. 41 42 21  24/05/2024 Asbestos “Asbestos” refers to a group of impure magnesium silicate minerals. Asbestos is a fibrous material. When inhaled, these fibers are highly toxic and carcinogenic. 43 The ability of the fibres to be woven along with their heat resistance and high tensile strength led to widespread applications of asbestos in fire- proofing materials, brake linings, prefabricated boards for construction, roofing tiles and insulation. 44 22  24/05/2024 Glass: What is glass? Glass is a state of matter. It is a solid produced by cooling molten material so that the internal arrangement of atoms, or molecules, remains in a random or disordered state, similar to the arrangement in a liquid. Figure 1. Structures of a typical solid (l.) and glass (r.) http://www.chemistryexplained.com/Ge-Hy/Glass.html 45 Glass: What is glass? Pure silica (from sand) can produce an excellent glass, but it is very high-melting (1,723 o C, or 3,133 o F), and the melt is so extremely viscous that it is difficult to handle. All common glasses contain other ingredients that make the silica easier to melt and the hot liquid easier to shape. http://www.chemistryexplained.com/Ge-Hy/Glass.html 46 23  24/05/2024 Making of glass Glass is made from liquid sand(formers) by heating ordinary sand, (which is mostly made of silicon dioxide) sodium carbonate(fluxes), and limestone(stabilizers) until it melts and turns into a liquid. Formers make up the largest percentage of the mixture to be melted. Fluxes lower the temperature at which the formers will melt. Stabilizers make the glass strong and water resistant. Calcium carbonate, often called calcined limestone, is a stabilizer. Without a stabilizer, water and humidity attack and dissolve glass 47 (Google images, 2018) When liquid silica cools, it forms a non-crystalline glass consisting of an infinite lattice assembled from SiO4 tetrahedra connected in a random manner. Only a few oxides form glasses (e.g. B2O3, SiO2, GeO2, P2O5 and As2O5) 48 24  24/05/2024 Types of Glasses Quartz glass (formed on cooling fused SiO2) can withstand sudden temperature changes and has specialist uses. Borosilicate glass (Pyrex) contains 10–15% B2O3 and has a lower melting point than silica glass. They are chemically unreactive and can stand great changes in temperature without breaking. 49 Types of Glasses Soda glass contains added alkali which converts some of the Si-O-Si bridges in the silica network into terminal Si=O groups, reducing the melting point below that of borosilicate glass. Lead crystal and flint glass are very dense and highly refractive glasses that are prepared by replacing lime with PbO and Pb3O4. 50 25  24/05/2024 Types of glass Coloured glasses made by adding additives such as transition metal compounds. For example- Cu2O, a red precipitate has been added to glass, to which it imparts a red color. CuO is used in making blue and green colored glass. CoO gives a blue glass FeO imparts a green color CaF2 produces an opaque white (milk) glass. (Google images, 51 2018) Glass: Obsidian Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian Yellow Obsidian Green Obsidian 52 Wikipedia, 2018 26