Metallic Bonds and Properties of Metals

Although metals are not ionic, they share several properties with ionic compounds. Properties of materials are based on bonding, and the bonding in both metals and ionic compounds is based on the attraction of particles with unlike charges. 

Although metals do not bond ionically, they often form lattices in the solid state. These lattices are similar to the ionic crystal lattices that were discussed in Section 8.2. In such a lattice, eight to 12 other metal atoms surround each metal atom. Although metal atoms have at least one valence electron, they do not share these electrons with neighboring atoms nor do they lose electrons to form ions. 

Properties of metals The typical physical properties of metals can be explained by metallic bonding. These properties provide evidence of the strength of metallic bonds. 

The melting points of metals vary greatly. Mercury is a liquid at room temperature, which makes it useful in scientific instruments such as thermometers and barometers. On the other hand, tungsten has a melting point of 3422°C, which makes it useful by itself or in combination with other metals 

The valence electrons in metals (shown in blue) are evenly distributed among the metallic cations (shown in red). Attractions between the positive cations and negative sea hold the metal atoms together in a lattice. 

The bonding in metals is explained by the electron sea model, which proposes that the atoms in a metallic solid contribute their valence electrons to form a sea of electrons that surrounds metallic cations. These delocalized electrons are not held by any specific atom and can move easily throughout the solid. A metallic bond is the attraction between these electrons and a metalUc cation. 

A mixture of elements that has metalUc properties is called an alloy. Alloys can be of two basic types. A substitutional alloy is one in which atoms of the original metal are replaced by other atoms of similar size. An interstitial alloy is one in which the small holes in a metallic crystal are filled by other smaller atoms. 

An unknown substance is found to be a good conductor of electricity when melted. Explain whether on this basis alone the substance can be classified as a metal. 

Suppose the substance in question 27 is allowed to solidify. It is then hammered, and shatters as a result. What property is being tested Would you classify this material as a metal Explain your answer. 

---

D. J. Vaughan and J. R. Craig, Mineral Chemistry of Metal Sulfides, Cambridge University Press, Cambridge, 1978, 493 pp. A comprehensive account of the structure bonding and properties of mineral sulfides. 

Theory that accounts for the bonding and properties of metallic solids. 

Chemists have prepared metal complexes containing metal atoms/ions as a means to understand better the structure, chemical bonding, and properties of metals and metal ions. One of the first efforts to affix these metal complexes to a surface as a means to create a supported catalyst was reported by Ballard followed by reports collected by Yermakov, et al. and Basset et al. We distinguish here between metal complexes that contain zero-valent metals and those that show metal cations and we limit this review to complexes containing metal ions as others have published extensive reviews of zero-valent, metal clusters and their chemistryIn our previous three reviews on the chemistry of supported, polynuclear metal complexes, we described efforts to synthesize and characterize oxide-supported, metal complexes as adsorbents, catalysts and precursors to supported metal oxides. In one application of this technology, efforts were... 

Ousters bridge the gap between small discrete molecules and infinitely extending solids. In this article, the structures, bonding, and properties of compounds which in a narrow sense do not even contain clusters but could be called normal salts or contaminated metals have been included. It is hoped that by taking this approach, though it might seem arbitrary in many respects, some contribution to a unified view on matter has been made. 

Phytosiderophores structures and properties of tnugineic acids and their metal complexes. Y. Sugiura and K. Nomoto, Struct. Bonding (Berlin), 1984,58,107 (50). 

The development of molecular orbital theory (MO theory) in the late 1920s overcame these difficulties. It explains why the electron pair is so important for bond formation and predicts that oxygen is paramagnetic. It accommodates electron-deficient compounds such as the boranes just as naturally as it deals with methane and water. Furthermore, molecular orbital theory can be extended to account for the structures and properties of metals and semiconductors. It can also be used to account for the electronic spectra of molecules, which arise when an electron makes a transition from an occupied molecular orbital to a vacant molecular orbital. 

The lobes of electron density outside the C-O vector thus offer cr-donor lone-pair character. Surprisingly, carbon monoxide does not form particularly stable complexes with BF3 or with main group metals such as potassium or magnesium. Yet transition-metal complexes with carbon monoxide are known by the thousand. In all cases, the CO ligands are bound to the metal through the carbon atom and the complexes are called carbonyls. Furthermore, the metals occur most usually in low formal oxidation states. Dewar, Chatt and Duncanson have described a bonding scheme for the metal - CO interaction that successfully accounts for the formation and properties of these transition-metal carbonyls. 

The Characterization and Properties of Small Metal Particles. Y. Takasu and A. M. Bradshaw, Surf. Defect. Prop. Solids p. 401 1978). 2. Cluster Model Theory. R. P. Messmer, in "The Nature of the Chemisorption Bond G. Ertl and T. Rhodin, eds. North-Holland Publ., Amsterdam, 1978. 3. Clusters and Surfaces. E. L. Muetterties, T. N. Rhodin, E. Band, C. F. Brucker, and W. R. Pretzer, Cornell National Science Center, Ithaca, New York, 1978. 4. Determination of the Properties of Single Atom and Multiple Atom Clusters. J. F. Hamilton, in "Chemical Experimentation Under Extreme Conditions (B. W. Rossiter, ed.) (Series, "Physical Methods of Organic Chemistry ), Wiley (Interscience), New York (1978). 

The development of the chemistry of carbene complexes of the Group 8a metals, Ru, Os, and Ir, parallels chemistry realized initially with transition metals from Groups 6 and 7. The pioneering studies of E. O. Fischer and co-workers have led to the characterization of many hundreds of carbene complexes in which the heteroatoms N, O, and S are bonded to the carbene carbon atoms. The first carbene ligands coordinated to Ru, Os, and Ir centers also contained substituents based on these heteroatoms, and in this section the preparation and properties of N-, O-, S-, and Se-substituted carbene complexes of these metals are detailed. 

Abstract Amino acids are the basic building blocks in the chemistry of life. This chapter describes the controllable assembly, structures and properties of lathanide(III)-transition metal-amino acid clusters developed recently by our group. The effects on the assembly of several factors of influence, such as presence of a secondary ligand, lanthanides, crystallization conditions, the ratio of metal ions to amino acids, and transition metal ions have been expounded. The dynamic balance of metalloligands and the substitution of weak coordination bonds account for the occurrence of diverse structures in this series of compounds. 

Most of the studies on organo-gallium, indium, and thallium porphyrin complexes have focused on synthesis and properties of the complexes, and rather little attention has been devoted to reaction chemistry. Two areas which have received some attention are the insertion of small molecules (SO2 or CO2) into the metal—carbon bonds and photochemical metal—carbon bond cleavage. The... 

---