DOCSLIB.ORG

Group Iv Elements

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Group Iv Elements GROUP IV ELEMENTS Group IV consists of Carbon – C, Silicon – Si, Germanium – Ge, Tin – Sn and Lead – Pb. This is one of the groups in which the transition from non-metals, C and Si through typical metalloid Ge, to weakly electropositive metals, Sn and Pb can be clearly seen. Valence shell – ns2np2 Table 1: Physical properties of Group IV elements Property C(6) Si(14) Ge(32) Sn(50) Pb(82) Electronic [He]2s22p2 [Ne]3s23p2 [Ar]3d104s24p2 [Kr]4d105s25p2 [Xe]4f145d106s26p2 configuration Electronegativity 2.5 1.74 2.0 1.7 1.55 IE(kJmol-1) 1st 1086 787 760 707 715 2nd 2352 1577 1534 1409 1447 3rd 4619 3230 3308 2943 3087 4th 6220 4355 4409 3821 4081 Melting pt (oC) 3550(diamond) 1410 937 232 328 Boiling pt (oC) 4827 2355 2830 2260 1744 Density (g cm-3) 3.51(diamond) 2.32 5.38 7.31 11.48 2.22(graphite) Occurrence Among all the elements of this group, carbon is the only one to occur in the elemental state as diamond and graphite. Silicon is the second most abundant element in the earth’s crust forming about 27.7%. Silicates are present in the rocks. Clays are essentially alumino-silicates of Na and Ca. Common sand is an impure form of silica. Glass is also a mixture of silicates. Germanium is a rare element. It occurs in traces in coal, in rare mineral argyrodite, 4Ag2S.GeS2, in germinate, Cu3(Ge.Fe)S4, and as admixture in zinc and tin ores. Tin occurs mainly as cassiterite or tin stone,SnO2 and Lead as galena, PbS. General characteristic and Important features of the Group 1. Carbon and silicon are outstanding but different. Carbon forms so many organic compounds; its chemistry is based on chains and rings of carbon atoms. Silicon forms many silicate rocks and its chemistry is dominated by polymeric silicate anions. This is due to their medium atomic size and their atomic configuration, ns2np2. In sp3 hybridization, all the four electrons become equivalent. Here their coordination number (4) is equal to the valence which gives the number of valence electrons which an atom uses in bonding. Thus, the resulting tetrahedral structures are also very symmetrical in their charge distribution since carbon and silicon have also medium electronegativities. 2. The properties of Ge, Sn and Pb change gradually as the group is descended, the metallic character increases down the group. 1 3. Oxidation state or valence They readily form tetravalent derivatives. However they show oxidn states of +2 and +4 which are also the valencies shown by these elements, except carbon where oxidation state varies from -4 to +4. 4+ All compound of +4 oxdn state are covalent because the IE to form M is too high to allow the formation of such ions. The heavier elements readily form lower oxidn state of +2; which become more ionic going down the group. Tin(II) and its compounds are often ionic. Only carbon forms anions due to its 2- 4- relatively high electronegativity, e.g., C2 in the carbides (acetylides) and C in methanides. 4. Coordination number: The maximum coordination number of carbon is four because it can never accommodate more than 8 electrons in its valence shell. Other members can expand the octet due to their d- orbitals. Thus, they can have higher coordination numbers and 2- 2- form complex ions e.g., SiF6 , PbCl4 etc. 5. Catenation: Is a property by virtue of which elements form long chins or rings compounds by single or multiple bond formation between atoms of the same element. The tendency to catenate decreases going down the group C, Si, Ge, Sn, Pb i.e., C> Si> Ge~ Sn> Pb catenation decrease Carbon shows this tendency to a remarkable extent because of its small size and high bond energy. Si and Ge to a lesser extent and Sn and Pb to a very small extent. E.g. Hydrides and halides Carbon: there are alkanes e.g. ethane, propane, butane, etc.of the formular CnH2n+2 n up to n= 100 are known. There are also others like alkenes and alkynes etc. Carbon also forms a number of catenated halides e.g., Polyvinylchlorides (PVC). Their formular is Cl (CH CH-) 2 n Silicon: forms silanes having the general formular SinH2n+2 where n≤ 8 Its halides also catenation and have a general formular SinX2n+2 Where if X=F, n= 1- 14 X = Cl, Br or I, n = 1 – 10 Germanium: forms germanes GenH2n+2, where n = 1 – 9 2 Halides form dimmers e.g., Ge2Cl6 Tin and Lead: while SnH4 & Sn2H6 have been prepared, preparation of PbH4 has failed. No catenated halides are known for Sn and Pb (6) Allotropy: The existence of elements in two or more different forms. These forms are called allotropes and the phenomenon is called allotropy. Allotropy occurs because of different crystal structures and shapes in the solid state and/ or combination of different numbers of atoms into molecules of simple compounds. Carbon: Has two forms (allotropes) namely diamond and graphite. They differ in their physical and chemical properties because of differences in their arrangement and bonding of the atoms i.e. they have different structures. They are, infact, macromolecules consisting of C atoms linked by a network of covalent bonds. Diamond: C 1.54Ao C C C C • Diamond structure consisting of carbon atoms surrounded by a tetrahedral arrangement of other carbon atoms at a distance of 1.54Ao. i.e. each carbon atom is tetrahedrally surrounded by four other carbon atoms which are covalently bonded to it. E(C-C) bond energy = 355kJmol-1 • Each C atom displays sp3 hybridization. • Since the structure possesses no free (mobile) electrons i.e. all valencies are satisfied (saturated); it behaves as an insulator and it is inert. • The rigid, strong three dimensional linkages make diamond one of the hardest substances known. • Since the covalent bonds must be broken before melting and boiling, it has an extremely high m.pt (3550oC) and b.pt (4827oC). 3 Graphite: 1.42Å First layer 3.35Å Second layer • Graphite has a two dimensional layer structure. Its lattice consists of plane layers or sheets in which carbon atoms are arranged in regular planar hexagons. • Carbon atoms are sp2 hybridized. Here each carbon atom is linked to other three carbon atoms through 3 bonds and one electron which has a overlap. This electron is delocalized over the whole planar layer. • These delocalized electrons make graphite a good conductor of electricity within the layer. Metallic lustre can also be attributed to these delocalized electrons. • Different layers are at a distance of 3.35Ao from each other and are thus held by weak Van der Waals forces only. These layers can slide over one another easily, imparting softness and slippery touch to graphite. Hence it is used as a lubricant and in pencil. • Due to its giant layer structure, it is very heat resistant and hence used for crucibles. • It is chemically very inert, thus, it is employed as an electrode material in many electrolyses. Silicon, Germanium & Lead: They exhibit only one allotropic form. Si and Ge crystallize in the diamond structure while Pb exhibit cubic closest- packed structure. Tin: Shows three modifications below its m.pt 232oC. They are interconvertible as shown in the following equilibrium: 4 – Sn – Sn – Sn 132oC 161oC HYDRIDES All the elements in group IV form covalent hydrides. The stability of the hydrides decreases down the group because of the decreasing M–H bond energies. Thus, while CH4 and other alkanes are stable compounds, PbH4 has not even been properly characterised, so far. Carbon: Why there are so many hydrocarbons in C? Because carbon undergoes catenation than any other element for both single and multiple bonds i.e., C – C, C = C and C C. This property is related to the bond strength E.g.: C-C = 346 kJmo-1 strong Si-Si = 226 kJmol-1 Ge-Ge = 186kJmol-1 -1 Sn-Sn = 151kJmol weak Catenated Pb compounds are unknown. The C–C bond strength is due to perfect overlap of the 2p orbitals which are also small in size hence intensive interaction. As the group is descended i.e. from Si to Pb the elements get larger and they possess d- orbitals. Thus, electrons partly diffuse into these vacant d- orbitals hence weak overlap of p orbitals. Si Ge Sn Pb further weaker Silicon, Tin and Lead: There are no silicon analogues of alkenes and alkynes (e.g. C2H4, C2H2). This is because poor overlap results from interaction of a 3p orbital of an atom of a 3rd period element and a 2p orbital of 2nd period or of two 3p orbitals of two atoms of the 3rd period elements. SinH2n+2 (n≤6) and GenH2n+2 (n≤6) are known. SnH4, Sn2H6 and PbH4 decompose slowly at room temperature and quickly when heated. 5 HALIDES All the elements of the group form dihalides (except carbon) and tetrahalides. All the four tetrahalides, namely, fluorides, chlorides, bromides and iodides are known for all the elements of the group, except PbBr4 and PbI4. Due to inert pair effect the stable oxidation state of Pb is +2. Therefore Sn and Pb form all the dihalides. Points to note: 2- • C–F, forms no complexes analogous to fluorosilicates SiF6 ions. This is attributed to the absence of d orbitals in the valence of carbon atom. Others have d orbitals available for coordination. • There is steady decrease in the C–X bond energies i.e., C-F>C-Cl>C-Br>C-I.
Load more

Recommended publications
  • Comparison of Sulfur to Oxygen*
    OpenStax-CNX module: m34977 1 Comparison of Sulfur to Oxygen* Andrew R. Barron This work is produced by OpenStax-CNX and licensed under the Creative Commons Attribution License 3.0 1 Size Table 1 summarizes the comparative sizes of oxygen and sulfur. Element Atomic radius Covalent radius Ionic radius (Å) van der Waal ra- (Å) (Å) dius (Å) Oxygen 0.48 0.66 1.40 1.52 Sulfur 0.88 1.05 1.84 1.80 Table 1: Comparison of physical characteristics for oxygen and sulfur. 2 Electronegativity Sulfur is less electronegative than oxygen (2.4 and 3.5, respectively) and as a consequence bonds to sulfur are less polar than the corresponding bonds to oxygen. One signicant result in that with a less polar S-H bond the subsequent hydrogen bonding is weaker than observed with O-H analogs. A further consequence of the lower electronegativity is that the S-O bond is polar. 3 Bonds formed Sulfur forms a range of bonding types. As with oxygen the -2 oxidation state prevalent. For example, sulfur forms analogs of ethers, i.e., thioethers R-S-R. However, unlike oxygen, sulfur can form more than two covalent (non-dative) bonds, i.e., in compounds such as SF4 and SF6. Such hypervalent compounds were originally thought be due to the inclusion of low energy d orbitals 3 2 in hybrids (e.g., sp d for SF6); however, a better picture involves a combination of s and p ortbitals in bonding (Figure 1). Any involvement of the d orbitals is limited to the polarization of the p orbitals rather than direct hydridization.
    [Show full text]
  • Group Vi Elements (The Chalcogens)
    GROUP VI ELEMENTS (THE CHALCOGENS) Elements are: - Oxygen-O, Sulphur-S, Selenium-Se, Tellurium-Te & Polonium-Po. Valence shell electronic configuration:- ns2np4 Compound formation:- O - S - covalent bonding Se - Te - tend to form ionic compound Po - down the group. Table 1: Some physical properties of Group VI elements. Property O(8) S(16) Se(34) Te(52) Po(84) Electronic [He]2s22p4 [Ne]3s23p4 [Ar]3d104s24p4 [Kr]4d105s25p4 [Xe]4f145d106s26p4 configuration 1st IE (kJmol-1) 1314 1000 941 869 813 Electronegativity 3.5 2.6 2.6 2.0 1.75 Melting pt. (oC) -229 114 221 452 254 Boiling pt (oC) -183 445 685 869 813 Density (gm-3) 1.14 2.07 4.79 6.25 9.4 Electron -141 -200 -195 -190 -183 affinity,E- Ionic radius M2- 1.40 1.85 1.95 2.20 2.30 /Ao Covalent 0.73 1.04 1.17 1.37 1.46 radius/Ao Oxidation states -2,-1,1,2 -2,2,4,6 -2,2,4,6 -2,2,4,6 2,4 Oxygen shows oxidation states of +1 and +2 in oxygen fluorides OF2 and O2F2 Occurrence:- Oxygen is the most abundant of all elements on earth. Dry air contains 20.946% oxygen by volume in the free form. Oxygen forms about 46.6% by weight of the earth’s crust including oceans and the atmosphere. Most of the combined oxygen is in the form of silicate, oxides and water. The abundance of sulphur in the earth’s crust is only 0.03-0.1%. it is often found as free element near volcanic regions.
    [Show full text]
  • This Ubiquitous Carbon…
    Engineering Physics Department Presents Dr. Cristian Contescu Senior Research Staff, Materials Science and Technology Division Oak Ridge National Laboratory This ubiquitous carbon… Abstract: After Stone Age, Bronze Age, and Iron Age, and after the Silicon Age of the informational revolution, the technologies of 21st century are marked by the ubiquitous presence of various forms of carbon allotropes. For a very long time, diamond and graphite were the only known carbon allotropes, but that has changed with the serendipitous discovery of fullerenes, carbon nanotubes, and graphene. Every ten or fifteen years scientists unveil new forms of carbons with new and perplexing properties, while computations suggest that the carbon’s family still has members unknown to us today. At a dramatically accelerated pace, new carbon forms find their place at the leading edge of scientific and technological innovations. At the same time traditional forms of carbon are being used in new and exciting applications that make our life safer, healthier, and more enjoyable. The 21st century may soon be recognized as the Age of Carbon forms. This educational talk will show how carbon, the fourth most abundant element in the Galaxy and the basis of life on Earth, was the engine of most important technological developments throughout the history of civilization. It will emphasize the ability of carbon atoms to generate a variety of mutual combinations and with many other chemical elements. These properties have placed carbon at the core of numerous inventions that define our civilization, while emerging new technologies open a rich path for value-added products in today’s market.
    [Show full text]
  • Properties of Carbon the Atomic Element Carbon Has Very Diverse
    Properties of Carbon The atomic element carbon has very diverse physical and chemical properties due to the nature of its bonding and atomic arrangement. fig. 1 Allotropes of Carbon Some allotropes of carbon: (a) diamond, (b) graphite, (c) lonsdaleite, (d–f) fullerenes (C60, C540, C70), (g) amorphous carbon, and (h) carbon nanotube. Carbon has several allotropes, or different forms in which it can exist. These allotropes include graphite and diamond, whose properties span a range of extremes. Despite carbon's ability to make 4 bonds and its presence in many compounds, it is highly unreactive under normal conditions. Carbon exists in 2 main isotopes: 12C and 13C. There are many other known isotopes, but they tend to be short-lived and have extremely short half-lives. Allotropes The different forms of a chemical element. Cabon is the chemical element with the symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. Carbon has 6 protons and 6 Source URL: https://www.boundless.com/chemistry/nonmetallic-elements/carbon/properties-carbon/ Saylor URL: http://www.saylor.org/courses/chem102#6.1 Attributed to: Boundless www.saylor.org Page 1 of 2 neutrons, and has a standard atomic weight of 12.0107 amu. Its electron configuration is denoted as 1s22s22p2. It is a solid, and sublimes at 3,642 °C. It's oxidation state ranges from 4 to -4, and it has an electronegativity rating of 2.55 on the Pauling scale. Carbon has several allotropes, or different forms in which it exists.
    [Show full text]
  • Basic Keyword List
    NOTICE TO AUTHORS 2008 Basic Keyword list A Antibodies Bismuth Chalcogens Ab initio calculations Antifungal agents Block copolymers Chaperone proteins Absorption Antigens Bond energy Charge carrier injection Acidity Antimony Bond theory Charge transfer Actinides Antisense agents Boranes Chelates Acylation Antitumor agents Borates Chemical vapor deposition Addition to alkenes Antiviral agents Boron Chemical vapor transport Addition to carbonyl com- Aqueous-phase catalysis Bridging ligands Chemisorption pounds Arene ligands Bromine Chemoenzymatic synthesis Adsorption Arenes Brønsted acids Chemoselectivity Aerobic oxidation Argon Chiral auxiliaries Aggregation Aromatic substitution C Chiral pool Agostic interactions Aromaticity C-C activation Chiral resolution Alanes Arsenic C-C bond formation Chirality Alcohols Arylation C-C coupling Chlorine Aldehydes Aryl halides C-Cl bond activation Chromates Aldol reaction Arynes C-Glycosides Chromium Alkali metals As ligands C-H activation Chromophores Alkaline earth metals Asymmetric amplification C1 building blocks Circular dichroism Alkaloids Asymmetric catalysis Cadmium Clathrates Alkanes Asymmetric synthesis Cage compounds Clays Alkene ligands Atmospheric chemistry Calcium Cleavage reactions Alkenes Atom economy Calixarenes Cluster compounds Alkylation Atropisomerism Calorimetry Cobalamines Alkyne ligands Aurophilicity Carbanions Cobalt Alkynes Autocatalysis Carbene homologues Cofactors Alkynylation Automerization Carbene ligands Colloids Allenes Autoxidation Carbenes Combinatorial chemistry Allosterism
    [Show full text]
  • Sp Carbon Chain Interaction with Silver Nanoparticles Probed by Surface Enhanced Raman Scattering
    sp carbon chain interaction with silver nanoparticles probed by Surface Enhanced Raman Scattering A. Lucotti1, C. S. Casari2, M. Tommasini1, A. Li Bassi2, D. Fazzi1, V. Russo2, M. Del Zoppo1, C. Castiglioni1, F. Cataldo3, C. E. Bottani2, G. Zerbi1 1 Dipartimento di Chimica, Materiali e Ingegneria Chimica ‘G. Natta’ and NEMAS - Center for NanoEngineered MAterials and Surfaces, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy 2 Dipartimento di Energia and NEMAS - Center for NanoEngineered MAterials and Surfaces, Politecnico di Milano, via Ponzio 34/3, I-20133 Milano, Italy 3 Actinium Chemical Research srl, via Casilina 1626/A, 00133 Roma, Italy and INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy Abstract Surface Enhanced Raman Spectroscopy (SERS) is exploited here to investigate the interaction of isolated sp carbon chains (polyynes) in a methanol solution with silver nanoparticles. Hydrogen-terminated polyynes show a strong interaction with silver colloids used as the SERS active medium revealing a chemical SERS effect. SERS spectra after mixing polyynes with silver colloids show a noticeable time evolution. Experimental results, supported by density functional theory (DFT) calculations of the Raman modes, allow us to investigate the behaviour and stability of polyynes of different lengths and the overall sp conversion towards sp2 phase. 1 2 1. Introduction Linear carbon chains with sp hybridization represent one of the simplest one dimensional systems and have therefore attracted a great interest for many years [1, 2]. sp chains can display two types of carbon-carbon bonding: polyynes, chains with single-triple alternating bonds (…-C≡C- C≡C-…) and polycumulenes, chains with all double bonds (…=C=C=C=…).
    [Show full text]
  • Agricultural Soil Carbon Credits: Making Sense of Protocols for Carbon Sequestration and Net Greenhouse Gas Removals
    Agricultural Soil Carbon Credits: Making sense of protocols for carbon sequestration and net greenhouse gas removals NATURAL CLIMATE SOLUTIONS About this report This synthesis is for federal and state We contacted each carbon registry and policymakers looking to shape public marketplace to ensure that details investments in climate mitigation presented in this report and through agricultural soil carbon credits, accompanying appendix are accurate. protocol developers, project developers This report does not address carbon and aggregators, buyers of credits and accounting outside of published others interested in learning about the protocols meant to generate verified landscape of soil carbon and net carbon credits. greenhouse gas measurement, reporting While not a focus of the report, we and verification protocols. We use the remain concerned that any end-use of term MRV broadly to encompass the carbon credits as an offset, without range of quantification activities, robust local pollution regulations, will structural considerations and perpetuate the historic and ongoing requirements intended to ensure the negative impacts of carbon trading on integrity of quantified credits. disadvantaged communities and Black, This report is based on careful review Indigenous and other communities of and synthesis of publicly available soil color. Carbon markets have enormous organic carbon MRV protocols published potential to incentivize and reward by nonprofit carbon registries and by climate progress, but markets must be private carbon crediting marketplaces. paired with a strong regulatory backing. Acknowledgements This report was supported through a gift Conservation Cropping Protocol; Miguel to Environmental Defense Fund from the Taboada who provided feedback on the High Meadows Foundation for post- FAO GSOC protocol; Radhika Moolgavkar doctoral fellowships and through the at Nori; Robin Rather, Jim Blackburn, Bezos Earth Fund.
    [Show full text]
  • Effect of Catenation and Basicity of Pillared Ligand on the Water Stability of Mofs
    Electronic Supplementary Material (ESI) for Dalton Transactions This journal is © The Royal Society of Chemistry 2013 SUPPORTING INFORMATION (SI) Effect of Catenation and basicity of Pillared Ligand on the Water Stability of MOFs Himanshu Jasuja, and Krista S. Walton* School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, USA * [email protected] EXPERIMENTAL SECTION 1. Characterization 1.1 PXRD (Powder X-Ray diffraction) patterns 14400 10000 6400 Intensity (counts) Intensity 3600 1600 400 0 5 10 15 20 25 30 35 40 45 50 2Theta (°) Figure S1: Comparison of PXRD pattern for as-synthesized Zn-BDC-DABCO or DMOF and its theoretical pattern from single crystal data Electronic Supplementary Material (ESI) for Dalton Transactions This journal is © The Royal Society of Chemistry 2013 14400 10000 6400 Intensity (counts) Intensity 3600 1600 400 0 5 10 15 20 25 30 35 40 45 50 2Theta (°) Figure S2: Comparison of PXRD pattern for as-synthesized Zn-BDC-BPY or MOF-508a and its theoretical pattern from single crystal data 14400 10000 6400 Intensity (counts) Intensity 3600 1600 400 0 5 10 15 20 25 30 35 40 45 50 2Theta (°) Figure S3: Comparison of PXRD pattern for as-synthesized Zn-TMBDC-DABCO or DMOF-TM and its theoretical pattern from single crystal data Electronic Supplementary Material (ESI) for Dalton Transactions This journal is © The Royal Society of Chemistry 2013 14400 10000 6400 Intensity (counts) Intensity 3600 1600 400 0 5 10 15 20 25 30 35 40 45 50 2Theta (°) Figure S4: Comparison of PXRD pattern for as-synthesized Zn-TMBDC-BPY or MOF- 508-TM and its theoretical pattern from single crystal data 6400 3600 Intensity (counts) Intensity 1600 400 0 10 15 20 25 30 35 40 45 2Theta (°) Figure S5: PXRD patterns for as-synthesized Zn-BDC-BPY or MOF-508a and activated Zn-BDC-BPY or MOF-508b displaying shifting of peaks towards right on activation which was also observed by Chen et.
    [Show full text]
  • Black Carbon and Its Impact on Earth's Climate
    Lesson Plan: Black Carbon and its Impact on Earth’s Climate A teacher-contributed lesson plan by Dr. Shefali Shukla, Sri Venkateswara College (University of Delhi), India. As a High School or Undergraduate Chemistry or Environmental Sciences teacher, you can use this set of computer-based tools to teach about allotropy, various allotropes of carbon and their structural and physical properties, black carbon, sources of black carbon and its impact on Earth’s climate. This lesson plan will help students understand the concept of allotropy and various allotropes of carbons. Students will learn about black carbon, the effect of black carbon on the Earth’s albedo and therefore, its impact on the climate. This lesson plan will also help students to understand how the immediate effect of controlling black carbon emission can potentially slow down the rate of global warming. Thus, the use of this lesson plan allows you to integrate the teaching of a climate science topic with a core topic in Chemistry or Environmental Sciences. Use this lesson plan to help your students find answers to: • What are allotropes? What are the various allotropes of carbon and their properties? • What are the sources of black carbon? • What are the different effects of black carbon on clouds? How does it modify rainfall pattern? • How does the deposition of black carbon on ice caps affect melting of the ice? • Explain how black carbon can have a cooling or warming effect on the planet? • What is the effect of black carbon on human health? About the Lesson Plan Grade Level: High School, Undergraduate Discipline: Chemistry, Environmental Sciences Topic(s) in Discipline: Allotropy, Allotropes of carbon, Black Carbon, Sources of Black Carbon, Heating and Cooling Effects of Black Carbon, Effect of Black Carbon on Human Health, Black Carbon Albedo, Black Carbon Emission Climate Topic: Climate and the Atmosphere, The Greenhouse Gas Effect, Climate and the Anthroposphere Location: Global Access: Online, Offline Language(s): English Approximate Time Required: 90-120 min 1 Contents 1.
    [Show full text]
  • Chemistry Study Materials for Class 10 (NCERT Based: Questions with Answers) Ganesh Kumar Date:- 28/07/2020
    Chemistry Study Materials for Class 10 (NCERT Based: Questions with Answers) Ganesh Kumar Date:- 28/07/2020 74. How much carbon is present on earth and CO2 in atmosphere? Answer: 0.02%, 0.03% 75. What is valency of carbon? Answer: 4 76. Why does carbon form strong bonds? Answer: It is due to small size. 77. What will be the product formed when carbon is burnt in presence of air? Answer: Carbon dioxide 78. What is Allotropy? Answer: It is a property due to which an element can exist in more than one form which differ in physical properties but have similar chemical properties, e.g., carbon, sulphur, phosphorus, oxygen show allotropy. 79. Name three allotropes of carbon. Answer: Diamond, graphite and Buckminster fullerenes 80. Which is the purest allotrope of carbon? Answer: Buckminster fullerenes. 81. Why is graphite soft and slippery? Answer: Due to weak vander Waals’ forces of attraction between hexagonal layers. 82. Why is diamond hard? Answer: It is due to strong covalent bonds. 83. Why is diamond lustrous? Answer: It is due to high refractive index. 84. Carbon has four electrons in its valence shell. How does carbon attain stable electronic configuration. Answer: By sharing four electrons with other atoms. 85. Why is carbon tetravalent? Answer: It is because carbon can share form electrons to complete its octet. 86. Which gas is present in LPG? Answer: Butane and Isobutane 87. Which element exhibits the property of catenation to maximum extent and why? Answer: Carbon shows catenation to maximum extent because it forms strong covalent bonds.
    [Show full text]
  • Introduction to Chemistry
    Introduction to Chemistry Author: Tracy Poulsen Digital Proofer Supported by CK-12 Foundation CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook Introduction to Chem... materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based Authored by Tracy Poulsen collaborative model termed the “FlexBook,” CK-12 intends to pioneer the generation and 8.5" x 11.0" (21.59 x 27.94 cm) distribution of high-quality educational content that will serve both as core text as well as provide Black & White on White paper an adaptive environment for learning. 250 pages ISBN-13: 9781478298601 Copyright © 2010, CK-12 Foundation, www.ck12.org ISBN-10: 147829860X Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made Please carefully review your Digital Proof download for formatting, available to Users in accordance with the Creative Commons Attribution/Non-Commercial/Share grammar, and design issues that may need to be corrected. Alike 3.0 Unported (CC-by-NC-SA) License (http://creativecommons.org/licenses/by-nc- sa/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), We recommend that you review your book three times, with each time focusing on a different aspect. which is incorporated herein by this reference. Specific details can be found at http://about.ck12.org/terms. Check the format, including headers, footers, page 1 numbers, spacing, table of contents, and index. 2 Review any images or graphics and captions if applicable.
    [Show full text]
  • Introduction to Phase Diagrams*
    ASM Handbook, Volume 3, Alloy Phase Diagrams Copyright # 2016 ASM InternationalW H. Okamoto, M.E. Schlesinger and E.M. Mueller, editors All rights reserved asminternational.org Introduction to Phase Diagrams* IN MATERIALS SCIENCE, a phase is a a system with varying composition of two com- Nevertheless, phase diagrams are instrumental physically homogeneous state of matter with a ponents. While other extensive and intensive in predicting phase transformations and their given chemical composition and arrangement properties influence the phase structure, materi- resulting microstructures. True equilibrium is, of atoms. The simplest examples are the three als scientists typically hold these properties con- of course, rarely attained by metals and alloys states of matter (solid, liquid, or gas) of a pure stant for practical ease of use and interpretation. in the course of ordinary manufacture and appli- element. The solid, liquid, and gas states of a Phase diagrams are usually constructed with a cation. Rates of heating and cooling are usually pure element obviously have the same chemical constant pressure of one atmosphere. too fast, times of heat treatment too short, and composition, but each phase is obviously distinct Phase diagrams are useful graphical representa- phase changes too sluggish for the ultimate equi- physically due to differences in the bonding and tions that show the phases in equilibrium present librium state to be reached. However, any change arrangement of atoms. in the system at various specified compositions, that does occur must constitute an adjustment Some pure elements (such as iron and tita- temperatures, and pressures. It should be recog- toward equilibrium. Hence, the direction of nium) are also allotropic, which means that the nized that phase diagrams represent equilibrium change can be ascertained from the phase dia- crystal structure of the solid phase changes with conditions for an alloy, which means that very gram, and a wealth of experience is available to temperature and pressure.
    [Show full text]