Lead atom

Lead, atomic number 82, is a member of Group 14 (IVA) of the Periodic Table. Ordinary lead is bluish grey and is a mixture of isotopes of mass number 204 (15%), 206 (23.6%), 207 (22.6%), and 208 (52.3%). The average atomic weight of lead from different origins may vary as much as 0.04 units. The stable isotopes are products of decay of three naturally radioactive elements (see Radioactivity, natural) comes from the uranium series (see Uraniumand... 

Fig. 10. Analysis of the atomic lattice images of the lead compound entering CNTs by capillary forces (a)detailed view of the high resolution image of the filling material, (b)tetragonal PbO atomic arrangement, note the layered structure and (c)tetragonal PbO observed in the [111] direction, note that the distribution of lead atoms follows the contrast pattern observable in (a), (d)bidimensional projection of the deduced PbO filling orientation inside CNTs as viewed in the tube axis direction, note that PbO layers are parallel to the cylindrical CNT cavity.

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. 

Lead (atomic radius = 0.181 nm) crystallizes with a face-centered cubic unit cell. What is the length of a side of the cell ... 

Predict the ground-state electron configuration of (a) a vanadium atom and (b) a lead atom. 

Although both aluminum and indium are in Group 13/III, aluminum forms A1J+ ions, whereas indium forms both In3+ and In+ ions. The tendency to form ions two units lower in charge than expected from the group number is called the inert-pair effect. Another example of the inert-pair effect is found in Group 14/IV tin forms tin(IV) oxide when heated in air, but the heavier lead atom loses only its two p-electrons and forms lead(II) oxide. Tin(II) oxide can be prepared, but it is readily oxidized to tin(IV) oxide (Fig. 1.56). Lead exhibits the inert-pair effect more strongly than tin. 

A very simple treatment can be carried out by assuming that the liquid phase is a series of ideal solutions of lead and thallium, and that in the solid phase isomorphous replacement of thallium atoms in the PbTl3 structure by lead atoms occurs in the way corresponding to the formation of an ideal solution. For the liquid phase the free energy would then be represented by the expression... 

There seem to be many binary metallic systems in which there are phases of this sort. In the sodium-lead system there are two such phases. One of them, based on the ideal structure Na3Pb, extends from 27 to 30 atomic percent lead, with its maximum at about 28 atomic percent lead and the other, corresponding to the ideal composition NaPb3, extends from 68 to 72 atomic percent lead, with maximum at about 70 atomic percent. The intensities of X-ray reflection have verified that in the second of these phases sodium atoms occupy the positions 0, 0, 0, and the other three positions in the unit cell are occupied by lead atoms isomorphously replaced to some extent by sodium atoms (Zintl Harder, 1931). These two phases are interesting in that the ranges of stability do not include the pure compounds Na8Pb and NaPb3. 

From other work on Pb(CH3)4 it is known that an Auger cascade connected with an L or M vacancy in the lead atom leads to the development of a charge of up to -t-17. This results in the total destruction of the molecule through a Coulomb explosion. On the basis of the 4/5 rule and the 14% internal conversion, one can estimate that for Pb(CH3)4 the molecule should remain intact in at least 69% of the decays, corresponding to the transformation ... 

A sample of lead atoms is analyzed by mass spectrometry. The bar graph in the margin shows the results. Use information from the graph to write the elemental symbol that represents each Pb isotope and estimate the natural abundance of each. List the number of protons and neutrons for each isotope. 

The values of Sp also behave systematically, as shown in Fig. 21, in which 5p is plotted against k for the various series B XY. It is evident that, for a given XY, Sp is an approximately linear function of k and hence of the strength of the interaction. Moreover, for a given B the order of 5p is IC1 > BrCl Br2 > CI2, which is the order of the polarisabilities of the leading atoms X in B XY and therefore seems reasonable from the definition (see earlier) of 5p. 

The picture shows one of the three natural decay series according to which heavy, radioactive nuclei eventually decay to stable lead atoms. 

Figure 2.5 (a) Hypothetical ionic molecule with spherical ions and the corresponding charge transfer moment, (b) In a real molecule the ions are polarized leading atomic dipoles in each atom that oppose the charge transfer moment. 

D. Double Bond Systems Containing a Lead Atom. 152... 

The ions having five tin or lead atoms are prepared by the reaction of a solution containing sodium and the cryptand reacting with alloys of sodium and tin or lead, respectively. It should also be mentioned that numerous derivatives of these materials have been prepared that contain alkyl and other groups. 

But the hexaphenylethane analog with lead atoms in the place of the central carbon atoms appears to be about 50% dissociated.36... 

The hexaphenyldilead radical anion almost certainly has a similar structure since the g values are all less than 2.0023. Calculation of the unpaired spin population in the lead 6s and 6p orbitals leads to values of 0.11 and 0.99. Once again the spin population is too large, especially for the 6p orbital. Nevertheless, the calculations do show that the spin density is probably entirely associated with the lead atoms. 

One doubly bidentate Lewis base 2,2 -bipyrimidine is coordinated with one germanium atom, while in the case of the analogous lead compound coordination takes place with two lead atoms. 

Organolead compounds with functionalized alkyl or aryl groups directly bound to the lead atom are useful synthetic tools in organolead chemistry. 

In the cation [Pb(15-crown-5)2]2+ the lead atom is sandwich-like coordinated by the ten oxygen atoms of the two crown ether molecules. (Figure 13). 

The X-ray crystal structure of Pb2(o-tolyl)6 shows one centrosymmetric molecule per unit cell. Figure 53 clearly shows that there is no expansion of coordination of the lead atom in Pb2(o-tolyl)6- The bond distances of the tetrahedral coordinated lead atom to the carbon atoms are in the range of 2.242-2.249 A the Pb—Pb distance was found to be... 

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