Chemical Bonding in Solids Ebook Free Download

Total Page:16

File Type:pdf, Size:1020Kb

Chemical Bonding in Solids Ebook Free Download CHEMICAL BONDING IN SOLIDS PDF, EPUB, EBOOK Jeremy K. Burdett | 336 pages | 30 Mar 1995 | Oxford University Press Inc | 9780195089929 | English | New York, United States Chemical Bonding in Solids PDF Book Half-fill three mL beakers with distilled water. One of the goals of this text is to bring Chemical Bonding in Solids examines how atoms in solids are bound together and how this determines the structure and properties of materials. In such a way, the participating atoms complete their octet or form stable noble gas electron configuration. Academic Skip to main content. Progress in Materials Science. Symmetry Considerations 4. Ionic Liquids Mark B. Given: compounds. Registroseg added it Sep 02, The tetrahedral array forms a giant network in which carbon atoms form six- membered rings. The metallic chemical bonding may be the collection of positive atomic cores and mobile electrons in the electron sea model. External Websites. Molecular solids and liquids with this type on bonding generally have higher melting points. That is, eight electrons in the outer energy level. Physical Properties and Chemical Bonding in Solids. The acceptor fills its outer electron shell by adding to it and the donor ends up with a full outer electron shell previously the filled shell beneath the partially-filled outer shell by donating the electrons in its unfilled outer shell. This demonstration provides experimental evidence on the nature of ionic and molecular substances in solution. Have students tear a sheet of paper into 16 pieces. In chemical reactions, do metals and nonmetals behave the same or differently with respect to sharing or transferring electrons? We expect C 6 CH 3 6 to have the lowest melting point and Ge to have the highest melting point, with RbI somewhere in between. Beginning with the halogen family, the valence electron shell has seven electrons, three pairs and one unpaired electron in s and p orbitals … for example, 3s 2 3px 2 3py 2 3pz 1 in chlorine. Our distribution centers are open and orders can be placed online. Classify Ge, RbI, C 6 CH 3 6 , and Zn as ionic, molecular, covalent, or metallic solids and arrange them in order of increasing melting points. Student answers will probably vary considerably. These forces can be viewed as due to motion of electrons and formation of temporary dipoles. Molecular Metals 4. A network covalent solid consists of atoms held together by a network of covalent bonds pairs of electrons shared between atoms of similar electronegativity , and hence can be regarded as a single, large molecule. Forgot your password? It's probable that students will not give complete answers without help from you. Many are very hard and quite strong. Chemical Bonding in Solids Writer The tetrahedral array forms a giant network in which carbon atoms form six-membered rings. State and apply the octet duet rule. Such solids are hard and rigid and have high melting points because the crystal is like one enormous molecule. Metallic bonds tend to be weakest for elements that have nearly empty as in Cs or nearly full Hg valence subshells, and strongest for elements with approximately half-filled valence shells as in W. Instead these electrons exist in molecular orbitals that are delocalized over many atoms, producing an electronic band structure. The structures and physical properties of intermetallic compounds are frequently quite different from those of their constituent elements, but they may be similar to elements with a similar valence electron density. The Third Rule 6. It thus has the zinc blende structure described in Section 8. That is, the faces should be the poles. Molecular solids The structures of molecular solids, which are solids composed of individual molecules, have also been touched on in the section on intermolecular forces. In contrast, intermetallic compounds An alloy that consists of certain metals that combine in only specific proportions and whose properties are frequently quite different from those of their constituent elements. Lewis in first proposed the formation of chemical bonds in the molecules by atoms without any transference of electron from one to other. The transfer of energy through the solid by successive collisions between the metal ions also explains the high thermal conductivity of metals. There exists a class of solids called network solids in which the bonding is essentially due to a network of covalent bonds that extends throughout the solid. The attractive interaction in a hydrogen bond typically has a strong electrostatic contribution, but dispersion forces and weak covalent bonding are also present. See Article History. By virtue of the rigidity of its bonding structure, diamond is the hardest substance known and also the best conductor of heat. Metallic solids are held together by a high density of shared, delocalized electrons, resulting in metallic bonding. Every lattice point in a pure metallic element is occupied by an atom of the same metal. The carbon atoms form six-membered rings. Chemical Bonding in Solids examines how atoms in solids are bound together and how this determines the structure and properties of materials. Lists with This Book. The melting points of metals, however, are difficult to predict based on the models presented thus far. Use the diagrams to write Lewis-dot formulas for these elements. The more electronegative atom electron acceptor accepts one or more valence electrons from the less electronegative atom electron donor. Structures of Soem AX2 Solids 7. Electrical Conductivity of Solutions … see page 1 b. Figure 6 illustrates this concept. Nonmetals, on the other hand, behave in the opposite manner, having higher electronegativities than metals. This model does not, however, explain many of the other properties of metals, such as their metallic luster and the observed trends in bond strength as reflected in melting points or enthalpies of fusion. The views of the atomists , however, lacked the authority that comes from experiment, and evidence of the existence of atoms was not forthcoming for two millennia until the emergence of quantitative, empirical science in the 18th century. The intermolecular attractions between the hydrogen atom and a lone pair of electrons on a N, O, or F atom from an adjacent molecule arising in this fashion are about an order of magnitude stronger than ordinary dipole- dipole bonding. Figure 8. The carbon atoms form six-membered rings. The hydrogen molecule is used to show that when two hydrogen atoms are close together, there's a possibility of more attractive forces than repulsive forces. The structure of crystalline quartz SiO 2 , shown in Section Academic Skip to main content. The compositions of most alloys can vary over wide ranges. The Fermi Surface 3. The traditional classification distinguishes four kinds of bonding: [1]. Rating details. The definition and formation of chemical bonds or bonding explain the different types of properties like polarity , dipole moment, electric polarization , oxidation number or state, etc of the ionic, covalent, metallic compounds in chemistry or science. Force at a Distance … see page 3. Chemical Bonding in Solids Reviews If the total energy of a group of atoms is lower than the sum of the energies of the component atoms, they then bond together and the energy lowering is the bonding energy. In metallic solids, the valence electrons are no longer exclusively associated with a single atom. For similar substances, the strength of the London dispersion forces increases smoothly with increasing molecular mass. Metallic solids are held together by a high density of shared, delocalized electrons, resulting in metallic bonding. Thus, metal atoms attract electrons less strongly and tend to lose electrons to acquire an octet noble gas electron configuration. Chemical Bonding in Ionic Compounds 4. Citation Type. Explain your reasoning. Atoms having a significant difference in electronegativity transfer electrons to form ionic bonds. Questions to consider What is the bonding geometry around each carbon? This article begins by describing the historical evolution of the current understanding of chemical bonding and then discusses how modern theories of the formation of chemical bonds have emerged and developed into a powerful description of the structure of matter. Their strength, stiffness, and high melting points are consequences of the strength and stiffness of the covalent bonds that hold them together. One of the goals of this text is to bring some of these ideas together and show how a broader picture exists once some of the prejudices which isolate one area from another are removed. Read more Therefore, the ionic bonding in the molecule is formed by the transfer of electron or electrons from an electropositive metal to an electronegative non-metal atom. Brass Cu and Zn in a ratio and bronze Cu and Sn in a ratio are examples of substitutional alloys An alloy formed by the substitution of one metal atom for another of similar size in the lattice. Some molecular solids, however, have significantly lower melting points than predicted by their molecular masses. For a detailed discussion of the structure and properties of atoms, see atom. In either case, use large diameter magnets for nuclei and small diameter magnets for electrons. Because all the atoms are the same, there can be no ionic bonding, yet metals always contain too few electrons or valence orbitals to form covalent bonds with each of their neighbors. There is a continuum between ionic solids and molecular solids with little ionic character in their bonding. State the characteristics of an ionic bond and recognize compounds having ionic bonds. The closeness of the packing of the atoms accounts for the high densities of metals. Chemical Bonding in Solids Read Online The basic ideas are illustrated in the lab involving chemical bonding in solids found on page 4. State and apply the octet duet rule.
Recommended publications
  • Bonding in Solids, Structural and Chemical Properties - R
    MATERIALS SCIENCE AND ENGINEERING – Vol. I – Bonding in Solids, Structural and Chemical Properties - R. W. Grimes BONDING IN SOLIDS, STRUCTURAL AND CHEMICAL PROPERTIES R. W. Grimes Imperial College, London, UK Keywords: Atomic structure, band structure, bonding, bulk modulus, conductivity, covalent, defects, electrons, energy level, hydrogen bonding, hybridization, insulators, ionic, metal, molecule, orbital, quantum, Schrödinger equation, semi-conductors, wave function. Contents 1. Introduction 2. Atomic Orbitals: their Origin and their Shapes 2.1. The Four Quantum Numbers 2.2. The Schrödinger Equation 2.3. Atoms with more than One Electron 3. Forming Bonds between like Atoms: Bonding and Anti-bonding Molecular Orbitals, Sigma and Pi-bonds 3.1. The Born-Oppenheimer Approximation 3.2. The Molecular Orbital Approximation 3.3. Linear Combination of Atomic Orbitals + 3.4. The Binding Curve for H2 3.5. Predicting the Stability of Other Simple Molecules 3.6. The Fluorine Diatomic Molecule: Another Homonuclear Molecule 4. Forming Bonds between Unlike Atoms: Polar Covalent and Ionic Bonds, Two Extremes of the Same Process 4.1. HF, a Polar Covalent Molecule 4.2. NaF, an Ionic Molecule 5. A Simple Model for an Ionic Solid: A Balance between Coulombic Attraction and Short-range Repulsion 5.1. Effective Potentials for Ionic Molecules 5.2. Extending the Model to Bulk NaF 5.3. CalculatingUNESCO the Bulk Modulus – EOLSS 6. From Hybridization to Conjugation to Band Structures: Why Diamond and Graphite have such Different Properties 6.1. Carbon 6.2. HybridizationSAMPLE and Molecular Orbitals CHAPTERS 7. More about Bands: Metals, Insulators and Semiconductors 7.1. Forming Bands in Metals 7.2.
    [Show full text]
  • BONDING in SOLIDS Engineering Physics
    Vignan BONDING IN SOLIDS Engineering Physics 1.1 Types of Bonding:- Different charge distributions in the atoms give rise to different types of bonding. They classified into five classes 1. Ionic bonding 2. Covalent bonding 3. Metallic bonding 4. Hydrogen bonding 5. Vander-Waals bonding Based on the bond strength atomic bonding can be grouped into “primary” and “secondary” bonding. Primary bonding:- Primary bonding have energies in the range of 1-10 eV. Ionic, covalent and metallic bonds are examples of primary bonding among these ionic and covalent bondings are generally stronger than the metallic bonding. Secondary bonding:- Secondary bonding have energies in the range of 0.01- 0.5 eV/ bond Hydrogen bonding and Vander Waals bonding are examples of secondary bonding. Generally, Vander Waals bonding is the weakest of all. 1 Vignan BONDING IN SOLIDS Engineering Physics 1.2 Ionic bonding (or) Hetro-Polar bond:- 1. Ionic bond is also called as “Hetro-Polar bond”. 2. Crystals in which ionic bond is present are known as “ionic crystals”. Ionic crystals are mostly insulating in character. Ex:-Nacl, NaBr, KBr, Mgo etc... 3. An Ionic bonding can only be formed between two different atoms, one electropositive and other electronegative. 4. Electropositive elements readily give up electrons and are usually group Ι (or) ΙΙ Elements e.g. Na, k, Ba. 5. Whereas electronegative elements readily take up electrons and are usually Group VΙ (or) VΙΙ elements e.g. Cl, Br and O. An example of the ionic bonding is NaCl. When neutral atom of a Na and Cl are brought close together it is easy for the valence electron of the sodium atom to be transferred to the chlorine atom so that both of them acquire a stable inert gas electronic configuration.
    [Show full text]
  • Representation of the States of Matter
    Chapter 10 Liquids & Solids Return to Slide 3 Representation of the states of Sublimation matter. Dry ice (solid CO2). Photo courtesy of American Color. PV = nRT ? ? Changes of State Intermolecular Forces • A change of state or phase transition is a Forces between (rather than within) molecules. change of a substance from one state to another. º dipole-dipole attraction: molecules with dipoles orient themselves so that “+” and gas “−” ends of the dipoles are close to each boiling condensation other. sublimation liquid condensation or º hydrogen bonds: dipole-dipole attraction in (see Figure 11.3) deposition which hydrogen is bound to a highly melting freezing electronegative atom. (F, O, N) solid 1 Hydrogen Bonding • Hydrogen bonding is a force that exists between a hydrogen atom covalently bonded to a very electronegative atom, X, and a lone pair of electrons on a very electronegative atom, Y. • To exhibit hydrogen bonding, one of the following three structures must be present. : : : H NOHFH • Only N, O, and F are electronegative enough to leave the hydrogen nucleus exposed. Dipole-Dipole Forces • Polar molecules can attract one another Figure 11.23: through dipole-dipole forces. Fluoromethane • The dipole-dipole force is an attractive and methanol. intermolecular force resulting from the tendency of polar molecules to align themselves positive end to negative end. δ+ H Cl δ− δ+ H Cl δ− Figure 11.21 shows the alignment of polar molecules. Hydrogen Bonding Figure 10.2: • A hydrogen atom bonded to an electronegative (a) The electrostatic interaction of two atom appears to be special. polar molecules. • The electrons in the O-H bond are drawn to the O (b) The interaction atom, leaving the dense positive charge of the of many dipoles in a hydrogen nucleus exposed.
    [Show full text]
  • Introduction • Bonding in Solids • Ionic Bond • Covalent Bond • Metallic Bond • Intermolecular Forces
    Topic 1: Introduction. Families of materials and applications Universidad Carlos III de Madrid MATERIALSCIENCIA E INGENIERÍA SCIENCE AND DE ENGINEERING MATERIALES www.uc3m.es TOPIC 1.2. BONDING IN SOLIDS. RELATION BETWEEN BONDING, STRUCTURE AND PROPERTIES OF MATERIALS • Introduction • Bonding in solids • Ionic bond • Covalent bond • Metallic bond • Intermolecular forces Dpt. Materials Sci. and Eng. and Chem. Eng. UC3M Sophia A. Tsipas / Dania Olmos 1 Topic 1: Introduction. Families of materials and applications INTRODUCTION Nature of bonding <> properties <> type of materials <> Processing and applications Applications Processing Structure Properties Dpt. Materials Sci. and Eng. and Chem. Eng. UC3M Sophia A. Tsipas / Dania Olmos 2 Topic 1: Introduction. Families of materials and applications IONIC BOND It forms between a metal and a non metal. There is electron transfer from the less electronegative atom to the more electronegative . Bonding forces ⇒ F electrostatic attraction between opposite charged ions. • Pure ionic bond: ideal. • ⇒ Always exists covalent participation Dpt. Materials Sci. and Eng. and Chem. Eng. UC3M Sophia A. Tsipas / Dania Olmos 3 Topic 1: Introduction. Families of materials and applications IONIC BOND Ionic compounds are crystalline solids It is a non directional bond formed by strong electrostatic interactions LATTICE ENERGY: Energy released when a mole of ionic solid is formed from its ions in the gas state. Born-Haber cycle for LiF. Step ΔH(kJ/mol) Na+ Sublimation of Li 155.2 Cl- Dissociation of F2 (g) 150.6 Ionization of Li(g) 520 - Gain of e of F(g) -328 Formation of LiF from Li(s) and -594.1 ½F2(g) Dpt. Materials Sci.
    [Show full text]
  • 1 Chemical Bonding in Solids
    j1 1 Chemical Bonding in Solids In this chapter, we discuss different mechanisms that can lead to bonding between atoms so that they form solids. We will encounter different cases such as ionic, covalent, or metallic bonding. It has to be kept in mind that these are just idealized limiting cases. Often mixed bonding types are found, for example, a combination of metallic and covalent bonding in the transition metals. As in conventional chemistry, only a restricted number of all the electrons participate in the bonding. These so-called valence electrons are the electrons in the outermost shell(s) of an atom. The electrons in the inner shells, or core electrons, are bound so tightly to the nucleus that they do not feel the presence of other atoms in their neighborhood. 1.1 Attractive and Repulsive Forces Two different forces must be present to establish bonding in a solid or in a molecule. An attractive force is necessary for any bonding. Different types of attractive forces are discussed below. A repulsive force, on the other hand, is required in order to keep the atoms from getting too close to each other. An expression for an interatomic potential can be written as A B f(r) ¼ À ; ð1:1Þ rn rm where n > m, that is, the repulsive part has to prevail for short distances (sometimes this is achieved by assuming an exponential repulsion potential). Such a potential and the resulting force are shown in Figure 1.1. The reason for the strong repulsion at short distances is the Pauli exclusion principle.
    [Show full text]
  • Chapter 2 Bonding in Solids
    2‐1 Chapter 2 Bonding in Solids Crystalline materials exhibit the complete spectrum of bond types: ionic, covalent, van der Waals, metallic. * In salts of complex anions, e.g. Li2SO4 have both ionic and covalent bonds. * Commonly, bonds are a blend of different types, e.g. TiO is ionic/metallic; CdI2 is ionic/covalent/van der Waals * In discussing structures, it is convenient to ignore temporarily the complexities of mixed bond types and to treat bonds as though they were purely ionic. Ionic bonding− structure with high symmetry and coordination number as high as possible, such that the electrostatic attractive force is maximized. Alkali and alkaline earth elements usually form ionic structures (Be is an exception), especially in combination with small electronegative anions such as O2- and F-. Covalent bonding− highly directional bonds irrespective of other atoms that are present, and CN is usually small. Covalent structure occur with (a) small atoms with high valence which, in the cationic state, would 3+ 4+ 4+ 4+ be highly polarizing 具極化能力, e.g. B , Si , P , S , etc.; (b) large atoms which in the anionic state are highly polarizable 易被極化但不丟電子, e.g. I-, S2-. Most non-molecular materials have mixed ionic and covalent bonding: * Ionicity ≡ percentage of ionic character in the bond * Transition metal compounds: the occurrence of metallic bonding 2‐2 2.1 Ionic bonding Purely ionic bonding rarely occurs. Even NaCl and CaO have some partial covalent character. The degree of covalent bonding increases with valence and ions with a net charge greater than +1 or −1 are unlikely to exist.
    [Show full text]
  • Bonding in Solids Bonding in Solids • There Are Four Types of Solid: 1
    Bonding in Solids Bonding in Solids • There are four types of solid: 1. Molecular (formed from molecules) - usually soft with low melting points and poor conductivity. 2. Covalent network -veryhardwithveryhigh melilting points and poor condiiductivity. 3. Ionic (formed form ions) - hard, brittle, high melting poitintsand poor condtiitductivity. 4. Metallic (formed from metal atoms) - soft or hard, high melting points, good conductivity, malleable and ductile. – NB: A solid with only one type of atom is also called ‘atomic’ Copyright © Houghton Mifflin Company. All rights reserved. 16a–1 Copyright © Houghton Mifflin Company. All rights reserved. 16a–2 Bonding in Solids Bonding in Solids Covalent Network Solids Covalent Network Solids • Intermolecular forces: dipole-dipole, London dispersion and H- bonds. • Atoms held together in large networks. • Exampp,gp,q(les: diamond, graphite, quartz (SiO2), silicon carbide ( SiC), and boron nitride (BN). • In diamond: – each C atom has a coordination number of 4; – each C atom is tetrahedral; – there is a three -dimensional array of atoms. – Diamond is hard, and has a high melting point (3550 °C). Copyright © Houghton Mifflin Company. All rights reserved. 16a–3 Copyright © Houghton Mifflin Company. All rights reserved. 16a–4 Diamond -Hard Structure - Tetrahedral atomic arrangement What hybrid state do you think the carbon has? Copyright © Houghton Mifflin Company. All rights reserved. 16a–5 Copyright © Houghton Mifflin Company. All rights reserved. 16a–6 Bonding in Solids Covalent Network Solids • In graphite – each C atom is arranged in a planar hexagonal ring; – layers of interconnected rings are placed on top of each other; – the distance between C atoms is close to benzene (1.42 ÅÅÅ vs.
    [Show full text]
  • Chemical Bonding in Crystals: New Directions
    Z. Kristallogr. 220 (2005) 399–457 399 # by Oldenbourg Wissenschaftsverlag, Mu¨nchen Chemical bonding in crystals: new directions Carlo Gatti* CNR-ISTM Istituto di Scienze e Tecnologie Molecolari, via Golgi 19, 20133 Milano, Italy Received November 8, 2004; accepted January 3, 2005 Chemical bonding / Crystals / Topological descriptors / Introduction QTAIMAC Quantum Theory of Atoms in Molecules and Crystals / ELF Electron Localization Function / Studies of chemical bonding in solids have experienced a Computational crystallography true blossoming over the past decade. The situation has clearly changed since when, in 1988, Roald Hoffman pro- Abstract. Analysis of the chemical bonding in the posi- vocatively observed [1] that “many solid chemists have tion space, instead of or besides that in the wave function isolated themselves from their organic or even inorganic (Hilbert) orbital space, has become increasingly popular for crystalline systems in the past decade. The two most colleagues by choosing not to see bonds in their materi- frequently used investigative tools, the Quantum Theory of als”. Many are the reasons behind this change and many Atoms in Molecules and Crystals (QTAIMAC) and the are the grafts from other scientific disciplines that have Electron Localization Function (ELF) are thoroughly dis- contributed to renovating the interest towards a local de- cussed. The treatment is focussed on the topological pecu- scription of bonding in solids beyond the tremendously liarities that necessarily arise from the periodicity of the successful, though empirical, Zintl–Klemm concept [2–4]. crystal lattice and on those facets of the two tools that A reason, on the one hand, is the continuously increasing have been more debated, especially when these tools are complexity (and reduced size) of new materials and the applied to the condensed phase.
    [Show full text]
  • Chapter 6 Cohesion (Bonding) in Solids
    Chapter 6 Cohesion (Bonding) in Solids 6.1 Introduction Solids often adopt well ordered crystalline structures with well defined lattice constants. Having discussed the many-body Hamiltonian of a solid and its calculation in some detail in previous chapters, it is now natural to ask why a given element chooses a particular crystal structure, and what kind of properties are connected with it. In particular, what types and strengths of forces, i.e. what bonds hold the solid together. This topic is called ’cohesion’ and it is very much to do with the nature of chemical bonding in solids. Just like in all previous chapters, we will restrict ourselves to the situation T 0K, i.e. suffi- ciently low temperatures. This is because at higher temperatures, the properties≈ of matter do not only follow from the total energy alone, but are also governed by other free energy contri- butions. Differing vibrational properties of different crystalline structures can induce structural phase transitions to other configurations upon heating. In fact most elements switch their crystal structure several times before they melt. Another issue is the configurational entropy e.g. due to defects such as vacancies interstials, and impurities. At low enough temperatures, however, the cohesive properties follow predominantly from the chemical binding in a perfect lattice, i.e. from the electrostatic interaction of the electron density with the ions and the ion-ion interac- tion. And this is what we will study in this chapter. The central property of low temperature cohesion is the cohesive energy Ecoh, which is the en- ergy needed to rip a sample apart into widely separated atoms.
    [Show full text]
  • Bonding in Solids & Crystal Structures and X-Ray Diffraction
    UNIT 1 Bonding in Solids & Crystal Structures and X-ray Diffraction 1.1 BONDING IN SOLIDS 1.1.1 INTRODUCTION The most convenient basis for solid state theory is a classification scheme based on the character of the interatomic bonding forces in various classes of crystalline materials. According to this scheme of classification, all solids fall into one of the five general categories: molecular, ionic, covalent, metallic and hydrogen bonded crystals. The distinction is not a sharp one, because some may belong to more than one class. It is a too fundamental fact that inert gases like helium, neon, argon, etc. exist in the atomic form and not easily combine with other atoms to form new compounds because of the magic number 2 in Helium and 8 in other cases. Interatomic force among the atoms in a solid is one of the tools to classify the solids and then to study their physical properties. 1.1.2 FORCES BETWEEN ATOMS AND BOND ENERGY The attractive electrostatic interaction between the electrons and positive charge of the nuclei is totally responsible to group them and then for holding together. Gravitational forces and magnetic forces are negligible compared with the said interaction. When two atoms (or ions) come close to one another, there will be repulsion between negatively charged electrons of both atoms. The repulsive force increases very rapidly as the distance of separation decreases. However when the distance of separation is large, there is attraction between positive nucleus and negative electrons. At some optimum distance (say r = ro), the attractive and repulsive forces just balance and hence the resultant force becomes 2 Applied Physics zero.
    [Show full text]
  • Bonding in Solids
    Module 6 : PHYSICS OF SEMICONDUCTOR DEVICES Lecture 32 : Bonding in Solids Objectives In this course you will learn the following Bonding in solids. Ionic and covalent bond. Structure of Silicon Concept of effective mass. Bonding in Solids Crystals can be classified on the basis of bonding of atoms to form a solid. There are primarily four types of bonding in solids, viz., molecular, ionic, covalent and metallic bonds. Molecular solids are formed by weak inter-molecular forces between molecules. Because of weak binding, the solids have low melting points Metallic solids are characterized by free electrons which move freely through the crystal being bonded to different atoms at different times. Ionic Bond In ionic solids, one of the specis of atoms donates electrons to another specis so that each of the atoms may become more stable by having a noble gas (octet) configuration of electrons. For instance in sodium chloride crystal, Sodium with an atomic number 11 has an electronic configuration while chlorine with the atomic number 17 has the configuration . When the atoms come together, Na gives away one electron and becomes positively ionized while Cl receives one electron and acquires a net negative charge. The negative an the positive ions are held together by electrostatic interaction. Ionic solids are hard, brittle, have high melting points and are poor electrical conductors. Covalent Bond Atoms can also achieve stable octet configuration by sharing of electrons. For instance, in forming hydrogen molecule a pair of hydrogen atoms share two electrons. Other examples of covalent bonded crystals are diamond, graphite, quartz (SiO ) etc.
    [Show full text]
  • Part II: Bonding in Solids 1 Van Der Waals Bonds
    Part II: Bonding in solids Since we are now familiar with the elements and their properties, we can start to discuss how they can be put together to create bigger structures – ultimately, we’re interested in crystalline solids. 1 Van der Waals bonds Let’s start with the noble elements, from group 8, and consider what are the possible interactions between two such atoms, for example two Ne atoms. At first sight, it would be tempting to say that they don’t interact at all with one another. As we’ve seen, because they have completely filled shells, they have very large ionization energies (it’s very hard to remove an electron away from them) and vanishing electron affinity (they don’t want an extra electron). So each Ne keeps its electrons in a filled spherical atomic shell, and what we have are two charge-neutral objects and no interactions (apart from gravitational attraction which is so weak that we can safely ignore it). This is not true, though. First, if we force the atoms close together by making the distance r between them smaller and smaller, it is clear that at some point the electronic clouds will start to overlap and at that point we should have very strong repulsion between them. This is because, according to Pauli’s principle, we can’t have electrons in the same place with the same spin, and that’s exactly what overlap of the electronic clouds would do if the electrons stay undisturbed in their inner shells. So when we bring the atoms close together, some of the electrons have to go into higher energy states and rearrange themselves to stay out of each other’s way, and this costs a lot of energy, leading to strong repulsion at very short distances.
    [Show full text]