Copper atomic properties

The Group 1 elements are soft, low-melting metals which crystallize with bee lattices. All are silvery-white except caesium which is golden yellow "- in fact, caesium is one of only three metallic elements which are intensely coloured, the other two being copper and gold (see also pp. 112, 1177, 1232). Lithium is harder than sodium but softer than lead. Atomic properties are summarized in Table 4.1 and general physical properties are in Table 4.2. Further physical properties of the alkali metals, together with a review of the chemical properties and industrial applications of the metals in the molten state are in ref. 11. 

The extrapolation of physical attributes of substances to the submicroscopic level of representation was evident when students explained the changes in the displacement reaction between zinc powder and aqueous copper(II) sulphate. The decrease in intensity of the blue colour of the solution was attributed by 31% of students to the removal of blue individual Cu + ions from aqueous solution. The suggestion that individual Cu + ions (the submicroscopic level) are blue may be indicative of the extrapolation of the blue colour of the aqueous copper(II) sulphate (the macroscopic level) to the colour of individual Cu + ions (the submicroscopic level). Thirty-one percent of students also suggested that reddish-brown, insoluble individual atoms of copper were produced in this chemical reaction, again suggesting extrapolation of the bulk properties of copper, i.e., being reddish-brown and insolnble in water (the macroscopic level), to individual copper atoms having these properties (the snbmicroscopic level). 

One way that a solid metal can accommodate another is by substitution. For example, sterling silver is a solid solution containing 92.5% silver and 7.5% copper. Copper and silver occupy the same column of the periodic table, so they share many properties, but copper atoms (radius of 128 pm) are smaller than silver atoms (radius of 144 pm). Consequently, copper atoms can readily replace silver atoms in the solid crystalline state, as shown schematically in Figure 12-4. 

Since ruthenium and rhodium are neighboring elements in the periodic table, a closer comparison of the properties of ruthenium-copper and rhodium-copper clusters is of interest (17). When we compare EXAFS results on rhodium-copper and ruthenium-copper catalysts in which the Cu/Rh and Cu/Ru atomic ratios are both equal to one, we find some differences which can be related to the differences in miscibility of copper with ruthenium and rhodium. The extent of concentration of copper at the surface appears to be lower for the rhodium-copper clusters than for the ruthenium-copper clusters, as evidenced by the fact that rhodium exhibits a greater tendency than ruthenium to be coordinated to copper atoms in such clusters. The rhodium-copper clusters presumably contain some of the copper atoms in the interior of the clusters. 

The properties of these complexes are well studied 126,132). Although monomeric in solution 126,133), they are dimeric in the solid state and a structural study of Cu(Et2copper atom lies 0.26 A out of the plane formed by four sulfur atoms at a distance of 2.30(1) A. A fifth, long Cu—S bond (2.85 A) is approximately perpendicular to this plane, whereas a hydrogen atom of an ethyl group is situated at the other side of the S4 plane at a distance of 2.86 A from the copper atom. 

On the basis of atomic properties, explain why copper forms solid solutions that can have the following percent of lattice sites containing the following atoms Ni 100%, A1 17%, and Cr <1%. 

Both the Einstein and Debye theories show a clear relationship between apparently unrelated properties heat capacity and elastic properties. The Einstein temperature for copper is 244 K and corresponds to a vibrational frequency of 32 THz. Assuming that the elastic properties are due to the sum of the forces acting between two atoms this frequency can be calculated from the Young s modulus of copper, E = 13 x 1010 N m-2. The force constant K is obtained by dividing E by the number of atoms in a plane per m2 and by the distance between two neighbouring planes of atoms. K thus obtained is 14.4 N m-1 and the Einstein frequency, obtained using the mass of a copper atom into account, 18 THz, is in reasonable agreement with that deduced from the calorimetric Einstein temperature. 

The insolubility of the Cu(I) halide salts, as well as the possibility of /x-halo-bridge formation between two copper atoms (as discussed later) or between the copper complex and the electrode surface, suggests that the presence of hahdes may alter the electrochemical properties observed for copper-containing solutions. 

Blue copper proteins in their oxidized form contain a Cu2+ ion in the active site. The copper atom has a rather unusual tetra-hedral/trigonal pyramidal coordination formed by two histidine residues, a cysteine and a methionine residue. One of the models of plastocyanin used in our computational studies (160) is pictured in Fig. 7. Among the four proteins, the active sites differ in the distance of the sulfur atoms from the Cu center and the distortion from an approximately trigonal pyramidal to a more tetrahedral structure in the order azurin, plastocyanin, and NiR. This unusual geometrical arrangement of the active site leads to it having a number of novel electronic properties (26). 

Spectral research permits us to obtain additional information about the role of the molecular structure in photoelectrical properties. The photosensitivity of the copper acetylenides is higher than in polymers with triple bonds without copper atoms. So the coordinating metal atoms and n-electrons of the acetylenic bonds play an important role in increasing the photosensitivity. 

The crystal structure of cupric acetate hydrate, Cu2(CH COO)4 2H20, shows that the pairs of copper atoms are only 2.64 A apart.50 This distance corresponds to a bond with n = 0.33. The substance has anomalous magnetic properties that have been interpreted as representing a weak bond.51 Similar bonds have been reported for several crystals containing Ni, Pd, and other metal atoms. 

The properties of the [CujI S - cluster are quite remarkable. This intense blue diamagnetic cluster (Amax 654 nm, e 46,100) can be described formally as a mixed-valence Cu(I), Cu(III) cluster (164). The crystal structure of this molecule (Fig. 59) supports this formalism and reveals a Cu5 rectangular pyramidal core (166). The basal copper atoms are three-coordinate and nearly planar and can be considered as Cu(I) units. The axial copper is four-coordinate and strictly planar, a coordination geometry appropriate for ad8 Cu(III) center. 

As best seen from Fig. 49 the structure of covellite CuS is composed of layers Cu+ — S2 — Cu+ which alternate with BN-like CuS layers. The latter are obviously responsible for the metallic properties of the CuS-type compounds. The diamagnetic CuS becomes superconducting at 1.62° K (215). Substitution of one third of the S by Se already shifts the transition to below 1° K (79). A replacement of the "divalent copper by nickel ( Cu2NiS3 ) failed (33). In the mineral idaite CusFeSg (507), however, one sixth of the copper atoms of CuS is replaced by iron atoms. 

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