Transition Metals

11 Key excerpts on "Transition Metals"

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  eBook - PDF

  General Chemistry: Atoms First

  • Young, William Vining, Roberta Day, Beatrice Botch(Authors)
  • 2017(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  AlbertSmirnov/iStockphoto.com 24 The Transition Metals Unit Outline 24.1 Properties of the Transition Metals 24.2 Isolation from Metal Ores 24.3 Coordination Compounds: Structure and Isomerism 24.4 Coordination Compounds: Bonding and Spectroscopy In This Unit… We have used our understanding of basic principles of chemistry to undertake brief explorations of the properties and reactivity of organic compounds and main-group elements, particularly those of the p -block elements. We now turn to the more complex chemistry of the Transition Metals, which consist of the metals found in Groups 3B-2B (Groups 3-12 in the IUPAC numbering system) of the periodic table. These elements play crucial roles in the manufacture of modern materials and in many important biological processes. In this unit we will examine how the metals are formed from their ores, used in alloys, and used to form coordination complexes, which are special types of Lewis acid–base compounds. Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 Unit 24 The Transition Metals 774 24.1 Properties of the Transition Metals 24.1a General Characteristics of Transition Metals Transition Metals are traditionally defined as the elements in Groups 3B-2B (3-12) of the periodic table. However, IUPAC defines transition elements as those elements whose atoms have partially filled d orbitals in their neutral or cationic state. Using this definition, the elements in Group 2B—zinc, cadmium, mercury, and copernicium—are not considered Transition Metals. However, in this unit we will occasionally include these elements in our discussion of the chemistry of the Transition Metals. Interactive Figure 24.1.1 shows the elements traditionally considered to be Transition Metals.

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  BIOS Instant Notes in Inorganic Chemistry

  • Tony Cox(Author)
  • 2004(Publication Date)
  • Taylor & Francis

    (Publisher)

  H1   INTRODUCTION TO Transition Metals

  Key Notes

  Scope	Transition elements form groups 3–11 in the d block. They have distinct chemical characteristics resulting from the progressive filling of the d shells. These include the occurrence of variable oxidation states, and compounds with structures and physical properties resulting from partially filled d orbitals.
  Vertical trends	Elements of the 3d series are chemically very different from those in the 4d and 5d series, showing weaker metallic and covalent bonding, stronger oxidizing properties in high oxidation states, and the occurrence of many more compounds with unpaired electrons.
  Horizontal trends	Electropositive character declines towards the right of each series. Elements become less reactive and their compounds show a tendency towards ‘softer’ behavior. Later elements in the 4d and 5d series are relatively more inert.
  Electron configurations	Neutral atoms have both s and d valence electrons, but in chemically important states are often regarded as having purely d n configurations.
  Related topics	Many-electron atoms (A3 ) The periodic table (A4 ) Trends in atomic properties (A5 )	Introduction to non-Transition Metals (G1 )

  Scope

  Transition Metals are elements of the d block that form compounds where electrons from d orbitals are ionized or otherwise involved in bonding. Typical transition metal characteristics include: the possibility of variable oxidation states; compounds with spectroscopic, magnetic or structural features resulting from partially occupied d

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  Understanding Bioanalytical Chemistry

  Principles and Applications

  • Victor A. Gault, Neville H. McClenaghan(Authors)
  • 2013(Publication Date)
  • Wiley

    (Publisher)

  3

  Transition Metals in health and disease

  Transition Metals comprise part of the d-block (groups 3–11) or middle portion of the Periodic Table of elements (see Appendix 2). The term transition metal arose as a result of their position in the Periodic Table and how they represent the transition between group 2 through to group 12 elements. Transition Metals are widely distributed throughout the earth and oceans, and play extremely important roles in nature. While Transition Metals are considered ‘trace elements’ in mammals, this by no means reflects their importance, and these metals play a key, often essential, role in many biological processes and, in particular, the catalysis of physiological enzymatic reactions. This chapter considers some of the core features of Transition Metals and their role in the regulation of normal physiological processes and the pathogenesis of disease.

  Learning Objectives

  • To describe and explain the structure and characteristics of key Transition Metals.
  • To outline and discuss the importance of Transition Metals in physiological processes.
  • To appreciate and convey the role of Transition Metals in disease processes.
  • To give examples to illustrate the therapeutic implications of Transition Metals.
  • To demonstrate knowledge of how Transition Metals are determined in nature.

  3.1 Structure and characteristics of key Transition Metals

  By the IUPAC (International Union of Pure and Applied Chemistry) definition, a transition metal is an element, an atom of which contains an incomplete d shell, or that gives rise to a cation with an incomplete d shell. Transition Metals have a total of nine atomic orbitals, but only some of these are used for bonding to ligands . Coordination number denotes the number of donor atoms associated with the central atom and dictates the shape, or stereochemistry , of the coordination complex

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  Chemistry, 5th Edition

  • Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  As we saw in the chapter on the atom, transition metal elements are sometimes called CHAPTER 13 Transition metal chemistry 627 the d-block elements, because the valence orbitals of these elements are d orbitals. We will see that the colours and magnetic properties of transition metal compounds can be explained in terms of the energies of the five d orbitals of the transition metal ion. Transition Metals are distinguished by their ability to form complexes. In these chemical species, transition metal ions (usually positively charged) are surrounded by one or more ions (almost always negatively charged) or neutral molecules, which are called ligands. When writing the formula of a transition metal complex, we enclose the metal and the bound ligands in square brackets (the metal ion first, followed by the ligands in alphabetical order), with the overall charge (if any) superscripted outside the brackets. The [Co(OH 2 ) 6 ] 2+ ion is a simple example of a transition metal complex, in which a single cobalt ion is bonded to six water molecules. The structure of this pink complex, which results from the dissolution of metallic cobalt in perchloric acid, is shown in figure 13.3a. In this complex, the cobalt ion has an oxidation state of +2, and is surrounded by six neutral H 2 O ligands to give an octahedral geometry about the metal ion. FIGURE 13.3 The structures of three transition metal complexes in which the cobalt ion has an oxidation state of +2: (a) the [Co(OH 2 ) 6 ] 2+ complex cation, (b) the [CoCl 4 ] 2- complex anion and (c) the [Co (CN) 5 ] 3- complex anion 2+ OH 2 H 2 O H 2 O OH 2 OH 2 OH 2 Co 2– Co Cl Cl Cl Cl 3– Co CN NC NC CN CN (a) [Co(OH 2 ) 6 ] 2+ (coloured pink) (c) (coloured yellow) [Co(CN 5 )] 3– (b) (coloured blue) [CoCl 4 ] 2– If we dissolve metallic cobalt in hydrochloric acid, rather than perchloric acid, we obtain a deep blue solution, due to the formation of the [CoCl 4 ] 2- complex anion.

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  Green and Sustainable Advanced Materials, Volume 2

  Applications

  • Shakeel Ahmed, Chaudhery Mustansar Hussain, Shakeel Ahmed, Chaudhery Mustansar Hussain(Authors)
  • 2018(Publication Date)
  • Wiley-Scrivener

    (Publisher)

  In the above reaction, the activation energy Ea is close to 435 KJ/ mole. However, when hydrogen is adsorbed by nickel, the breakage of the H-H bond is facilitated by a series of step.

  The activation energy is thus lowered due to the formation of Ni-H bonds. A change in activation energy, changes the rate of reaction.

  13.4 Transition Metals

  The largest group of elements on the periodic table is the Transition Metals. The transition elements are located in groups IB to VIIIB of the periodic table. They are found in the middle of the table and two rows of elements below the main body of the periodic table (the lanthanides and actinides) are special subsets of the Transition Metals. These metals are also known as the d-block elements. Thus, these are called “Transition Metals” because the electrons of their atoms make the transition to filling the d subshell or d sublevel orbital. Moving from left to right across the periodic table, the five d orbitals become more filled. The d electrons are loosely bound, which contributes to the high electrical conductivity and malleability of the transition elements. The transition elements have low ionization energies. They exhibit a wide range of oxidation states or positively charged forms. The positive oxidation states allow transition elements to form many different ionic and partially ionic compounds. The formation of complexes causes the d orbitals to split into two energy sublevels, which enables many of the complexes to absorb specific frequencies of light. Thus, the complexes form characteristic colored solutions and compounds. Complexation reactions sometimes enhance the relatively low solubility of some compounds.

  13.4.1 Common Properties of Transition Metals

  Along with basic characteristics (Table 13.1 ), these elements have some common properties such as:

  Table 13.1

  Summary of selected properties of Transition Metals.

  Element

  Symbol

  Atomicno.

  Atomicwt.

  Specificgravity

  Melting point °C

  Boiling point °C

  No. of isotopes1

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  Chemistry

  With Inorganic Qualitative Analysis

  • Therald Moeller(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Among the transitions that may occur are promotion of electrons from the d level to the higher s level or from the lower t 2 g to the higher e g energy level in complexes (called crystal-field transitions). There are some exceptions—for example, titanium(IV) compounds are usually colorless because the electrons are all paired and are not readily raised to higher energy levels. Many colorless ions are also found among the compounds of the second and third transition series, for example, [Pd(NH 3) 4 ] 2+ and [Pt(NH 3) 6 ] 4+. In such compounds the electrons are so tightly held that they are not readily raised to orbitals of higher energy. Another general property of d Transition Metals and their compounds is their high catalytic activity, which is usually due to the ease with which electrons are lost and gained or moved from one shell to another. Some typical applications of this property are the use of nickel as a hydrogenation catalyst, the ability of V 2 O 5 to serve as a catalyst in the contact process for the manufacture of sulfuric acid, and the use of MnO 2 in the catalytic decomposition of potassium chlorate. The catalytic activity of the Transition Metals and their compounds gives them great importance in the chemical industry. Chemists are always attempting to modify the rates of reactions by catalytic action. In many cases, the mechanism by which a well-known catalyst operates has not yet been discovered, and there is continuous effort to better understand how catalysts behave. In the meantime, empirical research is carried on in an attempt to improve the catalysts that are available or to find new and better ones

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  The Chemistry of the Metallic Elements

  The Commonwealth and International Library: Intermediate Chemistry Division

  • David J. Steele, J. E. Spice(Authors)
  • 2017(Publication Date)
  • Pergamon

    (Publisher)

  CHAPTER 8 The Transition Elements: their General Chemistry IN THE long version of the Periodic Table, between Groups Ila and Illb, there lies a block of elements known collectively as the transition elements. Precisely which elements are defined as transitional is, to a certain extent, a matter for personal opinion. There is general agreement that the term includes those elements having an incomplete d-or/-subshell of electrons. It will be seen from Table 8.1 that such a definition embraces all the elements in the block except the Group lib, the zinc triad, for these elements represent the stage where the inner shell is just filled. They there-fore show none of the characteristic properties associated with incomplete electron subshells. They have outer electronic structures similar to Group Ila: complete inner shells and two ^-electrons in the outer shell. For this reason there are marked similarities in the chemistry of the elements in the two Groups. The possession of a complete */-subshell bestows upon these elements properties which made it convenient to discuss them in the previous chapter. Elements of Group lb in oxidation states other than +1 (i.e. Cu +2 , Ag +2 , Au +3 ), in which the rf-electrons are used in bond formation, fall properly under the definition of transi-tional and will be discussed in this chapter. Certain other features of both Groups lb and lib will again be mentioned here to demonstrate transitional characteristics or to emphasise their disappearance when the rf-subshell is complete. The elements in Group Ilia, scandium, yttrium, lanthanum, and actinium have two ^-electrons in their outer shell and one ^/-electron in the penultimate shell; these three electrons are easily lost and the chemistry of the elements, especially scandium, is that of their tripositive ions, i.e. Sc(atom) ► Sc + + + +3e 3s 2 3p 6 3d 1 As 2 3s 2 3p 6 Scandium shows no transitional characteristics and might, with some justification, be 84

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  Inorganic Chemistry

  • William W. Porterfield(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Part Transition-Metal Compounds IV This page intentionally left blank The Properties of Transition Metals and Their Compounds Most of our discussion thus far has dealt with the structure and reactions of main- group elements— elements having s and p valence electrons only. The remainder of the book will be devoted to the chemistry of transition elements, those having valence d and/electrons. This perhaps seems a rather trivial distinction to make, but in fact this single change opens up entirely new types of orbital overlap and bonding, allowing the formation of compounds with quite different chemical properties. The inorganic chemist’s attraction has focused particularly on ^elec-tron transition elements, usually called simply the Transition Metals. The ^-elec-tron transition elements are usually known as lanthanides or rare earths; those with 5/ valence electrons are known as actinides. This chapter deals primarily with the J-electron Transition Metals, and makes a few comparisons with lan-thanides and actinides. We shall look at the nature of d orbitals and electrons, the bonding of these electrons in metals, the nature of the metals themselves, typical ionic lattices for the d block metals, and the basis for superconductor behavior in these lattices. Since the distinction between main-group metals and Transition Metals de-pends on the orbitals occupied, there is little difference in the properties of the pre-dominantly ionic compounds of the two groups. Ionic bonding, of course, can be described quite well on a “billiard-ball” basis without explicitly considering or-bitals or overlap. Table 10.1 suggests that the predominantly ionic transition-metal fluorides have much the same physical properties as the main-group ionic fluorides with the same metal charge and thus comparable lattice and solvation energies. For both groups, the chlorides are significantly less ionic, but the parallels are still quite strong.

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  Transition Metal Oxide Thin Film-Based Chromogenics and Devices

  • Pandurang Ashrit, Ghenadii Korotcenkov(Authors)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  U ).

  A special situation arises, however, when W   ∼

    U

  , in which the electrons are strongly correlated, as in the case of Transition Metals. The essential feature of such solids is that their behavior can be described only in terms of this electronic correlation. In TMOs we have the special case in which the localized and delocalized (itinerant ) outer shell electrons can be present simultaneously. Hence, the electronic properties of TMOs are better described in terms of strongly correlated electrons than in terms of the behavior of a single electron.

  The chemical classification scheme is based on the progressive filling of electrons into the valence shells. Following this classification rule, the periodic table is formed of s , p , d , and f blocks [3] . Of these, it is, generally, the elements with partially filled d subshells that are referred to as the transition elements . In free space, the outermost shells of transition metal atoms are formed of incomplete d shells and filled s shells. These can be Transition Metals formed of 3d , 4d , and 5d subshells partially filled with electrons. The partially filled orbitals of these metals lead to a fairly good thermal and electrical conductivity as well as to multiple oxidation states. Hence, the electron transfer between these states leads to very interesting optical, electrical, and magnetic properties as well as to their interesting applications in various fields. The oxides of Transition Metals are formed by combining one or more of the Transition Metals with oxygen atoms. These oxides are endowed with interesting features such as: (1) facile electron exchange with oxygen ions under very moderate activation energies, (2) a wide variety of bonding and multiple structures, (3) unusually high carrier density in certain phases, and more. Essentially, the oxygen atom, being an electronegative element with four electrons in its outer 2p shell, needs two electrons to complete this shell. The less electronegative Transition Metals with inner incomplete d shells and outer complete s shells lose two electrons to form the various TMOs [4 ,5 ]. By this exchange and covalent bond formation various TMOs, from monoxides (e.g., MnO), to dioxides (e.g., VO2 ), to trioxides (e.g., WO3 ), to higher and complex oxides such as perovskite (e.g., LaMnO3 ), can be formed, in which the transition metal gives off its s electrons and the required number of d electrons. This covalent bond formation in TMOs leaves the transition element with different numbers of d

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  Inorganic Chemistry for Geochemistry and Environmental Sciences

  Fundamentals and Applications

  • George W. Luther, III(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  Chapter 10 Transition Metals in Natural Systems

  10.1 Introduction

  Transition Metals are very important in many geochemical and biological processes. There are some important differences between the family members of the first transition series and those of the second and third transition series. Recall that the “d” orbitals for the second and third transition series metals are more diffuse so pairing of electron spins occurs more readily. Also, shielding of nuclear charge by inner electrons leads to higher IP and EA values (Table 3.6 ); thus, they tend to have higher effective nuclear charges for congeners with comparable electron configurations.

  In nature, the first transition series metals are typically characterized by and complexes, which exhibit tetrahedral, square planar, or octahedral geometry. In octahedral geometry, both high and low spin complexes are possible whereas square planar complexes are low spin and tetrahedral complexes are typically high spin. Although metal–metal bonds are known, they are much rarer than what is found in the second and third transition series metals. The metals are attacked or dissolved by dilute acids whereas the second and third transition series metals normally require concentrated oxidizing acids such as nitric acid alone or in combination with HCl (aqua regia). The second and third transition series metals form low spin complexes and exhibit coordination geometries of 4, 6, 7, and 8. There is a tendency for second and third transition series metals to form and remain in higher oxidation state compounds and ions than the first transition series metals. For example, molybdate as Mo(VI) is the dominant form of Mo in aquatic systems whereas chromate [with Cr(VI)] and Cr(III) exist in nature; Cr(III) converts to chromate when exposed to oxidants such as

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  Chemistry

  • John A. Olmsted, Gregory M. Williams, Robert C. Burk(Authors)
  • 2020(Publication Date)
  • Wiley

    (Publisher)

  KEY CONCEPTS: Many Transition Metals ( V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Mo) are essential for life. Metalloproteins may act as storage or transport agents, enzymes, or redox reagents. 19.5 Metallurgy Flotation Leaching Roasting Refining Ores Sulphides Impure oxides Ferroalloys Free metals Separation Conversion Reduction Refining Aqueous solution Impure chlorides Metal halides Pure chlorides Pure oxides Pure metals Froth of detergent- coated ore Ore/oil/ detergent mixture Compressed air Gangue (rock, sand) Stirring blade 1300 °C 1900 °C Molten iron 800 °C 1000 °C Molten slag Ore, limestone, coke LEARNING OBJECTIVE: Explain the chemistry of essential steps in the production of pure metals from ores. KEY CONCEPTS: Metallurgy includes separation, conver- sion, reduction, and refining steps. The starting material is an impure ore, and the end product is pure metal. Separation processes include flotation and leaching. Many sulphide ores are converted to oxides before reduction. 19.6 Applications of Transition Metals Ti Cr Cu Ag Au Zn Hg Pt metals Courtesy of Stephen Frisch James L. Amos/Corbis/ Getty Images LEARNING OBJECTIVE: Recognize the importance of tran- sition metals in everyday life. Learning Exercises 19.1 Write a description of the features that Transition Metals have in common. 19.2 Describe the features of the Transition Metals that are exploited in biology. Use an example to illustrate each feature. 19.3 Draw ball-and-stick models of all possible isomers of linear, tetrahedral, square planar, and octahedral complexes containing two different ligands. 19.4 Make a list of the Transition Metals discussed in this chapter and summarize their applications. 19.5 Write a summary of the biological chemistry of iron and copper described in this chapter. 19.6 List all terms new to you that appear in Chapter 19, and write a one-sentence definition of each in your own words. Consult the Glos- sary if you need help.

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