Bonding in Molecules Michaelmas Term - Second Year 2019 These 8 Lectures Build on Material Presented in “Introduction to Molecular Orbitals” (HT Year 1)
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Unit 3 Notes: Periodic Table Notes John Newlands Proposed an Organization System Based on Increasing Atomic Mass in 1864
Unit 3 Notes: Periodic Table Notes John Newlands proposed an organization system based on increasing atomic mass in 1864. He noticed that both the chemical and physical properties repeated every 8 elements and called this the ____Law of Octaves ___________. In 1869 both Lothar Meyer and Dmitri Mendeleev showed a connection between atomic mass and an element’s properties. Mendeleev published first, and is given credit for this. He also noticed a periodic pattern when elements were ordered by increasing ___Atomic Mass _______________________________. By arranging elements in order of increasing atomic mass into columns, Mendeleev created the first Periodic Table. This table also predicted the existence and properties of undiscovered elements. After many new elements were discovered, it appeared that a number of elements were out of order based on their _____Properties_________. In 1913 Henry Mosley discovered that each element contains a unique number of ___Protons________________. By rearranging the elements based on _________Atomic Number___, the problems with the Periodic Table were corrected. This new arrangement creates a periodic repetition of both physical and chemical properties known as the ____Periodic Law___. Periods are the ____Rows_____ Groups/Families are the Columns Valence electrons across a period are There are equal numbers of valence in the same energy level electrons in a group. 1 When elements are arranged in order of increasing _Atomic Number_, there is a periodic repetition of their physical and chemical -
Chemistry Third Marking Period Review Sheet Spring, Mr
Chemistry Third Marking Period Review Sheet Spring, Mr. Wicks Chapters 7-8: Ionic and Covalent Bonding • I can explain the difference between core electrons and valence electrons. • I can write Lewis dot symbols for atoms of particular elements and show the gain or loss of electrons to form ionic compounds. • I can compare and contrast ionic and molecular compounds. See Table 1. • I can describe ionic and covalent bonding and explain the differences between them. • I can compare and contrast the properties of ionic and molecular compounds. • I can predict trends in bond length when comparing carbon-carbon single, double, and triple bonds. Table 1: Comparing Ionic and Molecular Compounds Ionic Compounds Molecular Compounds Bonding Type: Ionic Bonding Covalent Bonding In this type of bonding, electrons are _____: Transferred Shared Type(s) of Elements Involved: Metal + Nonmetal Elements Nonmetal Elements Comparison of Larger Smaller electronegativity differences: Comparison of Properties: a. Melting and boiling points: a. Higher a. Lower b. Hardness: b. Harder b. Softer c. Conduction of electricity: c. When molten or dissolved in c. Molecular compounds do water, ionic compounds tend to not conduct electricity. conduct electricity. • I can apply trends for electronegativity in the periodic table to solve homework problems. • I can use electronegativity differences to classify bonds as nonpolar covalent, polar covalent, and ionic. See Table 2. Table 2: Classifying Bonds Using Electronegativity Differences Electronegativity Difference Bond Type 0 - 0.2 Nonpolar covalent bond 0.3 - 1.9 Polar covalent bond ≥ 2.0 Ionic bond Chemistry Third Marking Period Review Sheet, Page 2 • I can apply the octet rule to write Lewis structures for molecular compounds and polyatomic ions. -
Transition-Metal-Bridged Bimetallic Clusters with Multiple Uranium–Metal Bonds
ARTICLES https://doi.org/10.1038/s41557-018-0195-4 Transition-metal-bridged bimetallic clusters with multiple uranium–metal bonds Genfeng Feng1, Mingxing Zhang1, Dong Shao 1, Xinyi Wang1, Shuao Wang2, Laurent Maron 3* and Congqing Zhu 1* Heterometallic clusters are important in catalysis and small-molecule activation because of the multimetallic synergistic effects from different metals. However, multimetallic species that contain uranium–metal bonds remain very scarce due to the difficulties in their synthesis. Here we present a straightforward strategy to construct a series of heterometallic clusters with multiple uranium–metal bonds. These complexes were created by facile reactions of a uranium precursor with Ni(COD)2 (COD, cyclooctadiene). The multimetallic clusters’ cores are supported by a heptadentate N4P3 scaffold. Theoretical investigations indicate the formation of uranium–nickel bonds in a U2Ni2 and a U2Ni3 species, but also show that they exhibit a uranium–ura- nium interaction; thus, the electronic configuration of uranium in these species is U(III)-5f26d1. This study provides further understanding of the bonding between f-block elements and transition metals, which may allow the construction of d–f hetero- metallic clusters and the investigation of their potential applications. ultimetallic molecules are of great interest because of This study offers a new opportunity to investigate d− f heteromul- their fascinating structures and multimetallic synergistic timetallic clusters with multiple uranium–metal bonds for small- Meffects for catalysis and small molecule activation1–7. Both molecule activation and catalysis. biological nitrogen fixation and industrial Haber–Bosch ammonia syntheses, for example, are thought to utilize multimetallic cata- Results and discussion lytic sites8,9. -
Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. -
Quintuple Bond
Quintuple bond A quintuple bond in chemistry is an unusual type of chemical bond first observed in 2005 in a chromium dimer in an organometallic compound. Single bonds, double bonds and triple bonds are commonplace in chemistry. Quadruple bonds are rare but can be found in some Quintuple bonding. Article By: Kempe, Rhett Department of Inorganic Chemistry II, Universität Bayreuth, Bayreuth, Germany. Bond orders, formally the number of electron pairs that contribute positively to a chemical bond between atoms, matter fundamentally. This becomes obvious by considering the simple hydrocarbons ethane, ethylene, and acetylene, which have a bond order of one, two, and three, respectively. All three consist of two carbon atoms linked via a single, double, or triple bond. A quintuple bond in chemistry is an unusual type of chemical bond, first reported in 2005 for a dichromium compound. Single bonds, double bonds, and triple bonds are commonplace in chemistry. Quadruple bonds are rarer but are currently known only among the transition metals, especially for Cr, Mo, W, and Re, e.g. [Mo2Cl8]4− and [Re2Cl8]2−. In a quintuple bond, ten electrons participate in bonding between the two metal centers, allocated as σ2Ï4δ4. A quintuple bond in chemistry is an unusual type of chemical bond, first reported in 2005 for a dichromium compound. Single bonds, double bonds, and triple bonds are commonplace in chemistry. Quadruple bonds are rarer but are currently known only among the transition metals, especially for Cr, Mo, W, and Re, e.g. [Mo2Cl8]4− and [Re2Cl8]2−. In a quintuple bond, ten electrons participate in bonding between the two metal centers, allocated as σ2Ï4δ4. -
Periodic Trends Lab CHM120 1The Periodic Table Is One of the Useful
Periodic Trends Lab CHM120 1The Periodic Table is one of the useful tools in chemistry. The table was developed around 1869 by Dimitri Mendeleev in Russia and Lothar Meyer in Germany. Both used the chemical and physical properties of the elements and their tables were very similar. In vertical groups of elements known as families we find elements that have the same number of valence electrons such as the Alkali Metals, the Alkaline Earth Metals, the Noble Gases, and the Halogens. 2Metals conduct electricity extremely well. Many solids, however, conduct electricity somewhat, but nowhere near as well as metals, which is why such materials are called semiconductors. Two examples of semiconductors are silicon and germanium, which lie immediately below carbon in the periodic table. Like carbon, each of these elements has four valence electrons, just the right number to satisfy the octet rule by forming single covalent bonds with four neighbors. Hence, silicon and germanium, as well as the gray form of tin, crystallize with the same infinite network of covalent bonds as diamond. 3The band gap is an intrinsic property of all solids. The following image should serve as good springboard into the discussion of band gaps. This is an atomic view of the bonding inside a solid (in this image, a metal). As we can see, each of the atoms has its own given number of energy levels, or the rings around the nuclei of each of the atoms. These energy levels are positions that electrons can occupy in an atom. In any solid, there are a vast number of atoms, and hence, a vast number of energy levels. -
Fragment Orbitals for Transition Metal Complexes
Fragment Orbitals for Transition Metal Complexes Introduction • so far we have concentrated on the MO diagrams for main group elements, and the first 4 lectures will link into your Main Group chemistry course • now we will concentrate on the MO diagrams for TM complexes, and the next 4 lectures will link into your TM and Organometallic and your Crystal Architecture chemistry courses • areas we don’t have the space to cover are cluster MOs (very interesting!) and extended system MOs (solid state, polymers, conjugated systems). However with the knowledge gained from this course you should be able to delve into these areas if you are interested Fragment Orbitals of the Metal • transition metals (TM) are electropositive thus the valence FAOs are high in energy • the energy levels included for the TMs differ from the main group o the active electrons for bonding are in the 3d (or 4d) shell, and thus these AOs are included in the valence MO diagram o the occupied 3s and 3p AOs are too deep in z energy to participate in bonding and are ignored L o however the vacant 4s and 4p AOs are very close L L in energy to the 3dAOs and we do include these y M x AOs in valence MO diagrams that include TMs L L • the symmetry labels s, p and d refer to spherical L symmetry and in any MO diagram the new Figure 1 coordinate system symmetry labels for the TM AOs must be IMPORTANT determined using the point group symmetry of the 4p t ! 1u molecule and your character tables o for example, metals are often in an octahedral environment (six coordinating ligands, -
Coniguring New Bonds Between Irst-Row Transition Metals
Physical Sciences ︱ Professor Connie Lu Decreasing M-Cr bond order Coniguring new bonds 28 25 26 27 Ni between irst-row Mn Fe Co 24 24 24 24 transition metals Cr Cr Cr Cr Transition metals are some of the B.O.= 5 3 2 1 most important elements in the Periodic Table for their wealth of applications, spanning catalysis to biology. The rich chemistry of molecules composed of ten or more Building metal-metal bonds can be like building blocks – chemical bonding to chromium (Cr) the transition metals arises from atoms. Ligands can be diverse not just can change from quintuple to single by varying the other light transition metal partner. their remarkable ability to form in their chemical structure, but also in multiple chemical bonds, a process how they attach to the metal centre. Professor Lu wants to ind ways to exploit that is still not fully understood Some ligands just bind directly to the and remains a major challenge in metal whereas others bind through Professor the properties of the more common light fundamental chemistry. multiple sites on the ligand, or in the Connie Lu at the University of case of metal complexes with more than transition metals, to replace their heavier, Minnesota has been tackling this one metal centre, the ligands can act as question by synthesising the irst a bridge between the centres by binding scarcer counterparts mixed-metal complex containing the two metals together. synthesis and carbon dioxide activation, This is why Professor Lu wants to only the irst-row transition metals an important step in the development ind ways to exploit the properties to explore the fundamental nature It is the variety and the complexity of this of sustainable energy technologies. -
The Dicarbon Bonding Puzzle Viewed with Photoelectron Imaging
The dicarbon bonding puzzle viewed with photoelectron imaging The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Laws, B.A., et al., "The dicarbon bonding puzzle viewed with photoelectron imaging." Nature Communications 10 (Nov. 2019): no. 5199 doi 10.1038/s41467-019-13039-y ©2019 Author(s) As Published 10.1038/s41467-019-13039-y Publisher Springer Science and Business Media LLC Version Final published version Citable link https://hdl.handle.net/1721.1/125929 Terms of Use Creative Commons Attribution 4.0 International license Detailed Terms https://creativecommons.org/licenses/by/4.0/ ARTICLE https://doi.org/10.1038/s41467-019-13039-y OPEN The dicarbon bonding puzzle viewed with photoelectron imaging B.A. Laws 1*, S.T. Gibson 1, B.R. Lewis1 & R.W. Field 2 Bonding in the ground state of C2 is still a matter of controversy, as reasonable arguments may be made for a dicarbon bond order of 2, 3,or4. Here we report on photoelectron spectra À of the C2 anion, measured at a range of wavelengths using a high-resolution photoelectron 1Σþ fi 3Π 1234567890():,; imaging spectrometer, which reveal both the ground X g and rst-excited a u electronic states. These measurements yield electron angular anisotropies that identify the character of two orbitals: the diffuse detachment orbital of the anion and the highest occupied molecular orbital of the neutral. This work indicates that electron detachment occurs from pre- σ π dominantly s-like (3 g) and p-like (1 u) orbitals, respectively, which is inconsistent with the predictions required for the high bond-order models of strongly sp-mixed orbitals. -
Octet Rule & Ions
Chemistry 51 Chapter 5 OCTET RULE & IONS Most elements, except noble gases, combine to form compounds. Compounds are the result of the formation of chemical bonds between two or more different elements. In the formation of a chemical bond, atoms lose, gain or share valence electrons to complete their outer shell and attain a noble gas configuration. This tendency of atoms to have eight electrons in their outer shell is known as the octet rule. Formation of Ions: An ion (charged particle) can be produced when an atom gains or loses one or more electrons. A cation (+ ion) is formed when a neutral atom loses an electron. An anion (- ion) is formed when a neutral atom gains an electron. 1 Chemistry 51 Chapter 5 IONIC CHARGES The ionic charge of an ion is dependent on the number of electrons lost or gained to attain a noble gas configuration. For most main group elements, the ionic charges can be determined from their group number, as shown below: All other ionic charges need to be memorized and known in order to write correct formulas for the compounds containing them. 2 Chemistry 51 Chapter 5 COMPOUNDS Compounds are pure substances that contain 2 or more elements combined in a definite proportion by mass. Compounds can be classified as one of two types: Ionic and molecular (covalent) Ionic compounds are formed by combination of a metal and a non-metal. The smallest particles of ionic compounds are ions. Molecular compounds are formed by combination of 2 or more non-metals. The smallest particles of molecular compounds are molecules. -
Multiple Bonds in Novel Uranium-Transition Metal Complexes
Multiple Bonds in Novel Uranium-Transition Metal Complexes Prachi Sharma,†,‡ Dale R. Pahls, †,‡ Bianca L. Ramirez, † Connie C. Lu, † and Laura Gagliardi†,‡,* †Department of Chemistry and ‡Minnesota Supercomputing Institute & Chemical Theory Center, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States Abstract Novel heterobimetallic complexes featuring a uranium atom paired with a first-row transition metal have been computationally predicted and analyzed using density functional theory and multireference wave-function based methods. The synthetically i i inspired metalloligands U( Pr2PCH2NPh)3 (1) and U{( Pr2PCH2NAr)3tacn} (2) are explored in this study. We report the presence of multiple bonds between uranium and chromium, uranium and manganese, and uranium and iron. The calculations predict a i five-fold bonding between uranium and manganese in the UMn( Pr2PCH2NPh)3 and − UMn(CO)3 complexes which is unprecedented in the literature. 1. Introduction Metal-metal bonding is a fundamental concept in chemistry that affects the properties of the systems of interest and is instrumental to understanding structure and reactivity, metal-surface chemistry, and metal-based catalysis.1 Compared to transition metals, the nature of metal-metal bonds involving f-block metals, especially the actinide series, has been less explored.2 The 5f orbitals of the actinides, such as uranium, have suitable spatial extension to participate in bonding that makes the d – f heterobimetallic bond an interesting target to improve our understanding of the interplay of the d and f orbitals. Reviewing both theoretical and experimental data in the literature, very few examples have been reported for bonding between an actinide, such as uranium and a transition 1 metal to date. -
Visualizing Molecules - VSEPR, Valence Bond Theory, and Molecular Orbital Theory
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Visualizing Molecules - VSEPR, Valence Bond Theory, and Molecular Orbital Theory Nestor S. Valera 1 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Visualizing Molecules 1. Lewis Structures and Valence-Shell Electron-Pair Repulsion Theory 2. Valence Bond Theory and Hybridization 3. Molecular Orbital Theory 2 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The Shapes of Molecules 10.1 Depicting Molecules and Ions with Lewis Structures 10.2 Valence-Shell Electron-Pair Repulsion (VSEPR) Theory and Molecular Shape 10.3 Molecular Shape and Molecular Polarity 3 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 10.1 The steps in converting a molecular formula into a Lewis structure. Place atom Molecular Step 1 with lowest formula EN in center Atom Add A-group Step 2 placement numbers Sum of Draw single bonds. Step 3 valence e- Subtract 2e- for each bond. Give each Remaining Step 4 atom 8e- valence e- (2e- for H) Lewis structure 4 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Molecular formula For NF3 Atom placement : : N 5e- : F: : F: : Sum of N F 7e- X 3 = 21e- valence e- - : F: Total 26e Remaining : valence e- Lewis structure 5 Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SAMPLE PROBLEM 10.1 Writing Lewis Structures for Molecules with One Central Atom PROBLEM: Write a Lewis structure for CCl2F2, one of the compounds responsible for the depletion of stratospheric ozone.