Ionization energies electronegativity and atomic

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Unformatted text preview: osphorus chemistry. Ionization energies, electronegativity, and atomic radii are compared with those of N, As, S b and Bi on p. 550. White phosphorus ( aP4) has mp 44.1" (or 44.25" when ultrapure), bp 280.5" and a vapour pressure of 0.122 mmHg at 40°C. It is an insulator with an electrical resistivity of -10" ohm cm at 11"C, a dielectric constant of 4.1 (at 20") and a refractive index n~ (29.2") 1.8244. The heat of combustion of P4 to P4O10 is -2971 kJmol-' and the heat of transition to amorphous red phosphorus is -29 k (mol Pq)-*. J 12.2.5 Chemical reactivity and stereochemistry The spontaneous chemiluminescent reaction of white phosphorus with moist air was the first property of the element to be observed and was the origin of its name (p. 473); its spontaneous ignition temperature in air is -35". We have already seen (p. 481) that the reactivity of phosphorus depends markedly upon which allotrope is being studied and that increasing catenation of the polymeric red and black forms notably diminishes both reactivity and solubility. The preference of phosphorus for these forms rather than for the gaseous form Pz, which is its most obvious distinction from nitrogen, can be rationalized in terms of the relative strengths of the triple and single bonds for the 2 elements. Reliable values are hard to obtain but generally accepted values are as follows: J > E(N=N)flcl E (per mol<of N N -N )/kJ per mol of N Ratio 159 (or 296) 5.95 (or 3.20) E(P-P)kJ E()P-P<)/kJ per mol of P Ratio 2.45 It is clear that, for nitrogen, the triple bond is preferred since it has more than 3 times the energy of a single bond, whereas for phosphorus the triple-bond energy is less than 3 times the singlebond energy and so allotropes having 3 single bonds per P atom are more stable than that with a triple bond. Ch. 12 Phosphorus 484 Table 12.2 Stereochemistry of phosphorus CN Geometry 0 1 Examples - - 2 Bent('*) 3 Planar 4 Pyramidal Tetrahedral 5 6 7 8 9 Local CzV Trigonal bipyramidal Square pyramidal Octahedral Trigonal primsatic + Irregular (4 2) Capped trigonal prismatic Cubic Bicapped trigonal prismatic Tricapped trigonal prismatic Monocapped square antiprismatic P(g) - in equilibrium with P2(g) above 2200°C P2(g) - in equilibrium with P4(g) above 800°C; HC-P; FC-P; MeC-P (p. 544) HP=CH2,(29) [P(CN)2]-,'30' [(C&4S(NR)C}2P]+X- (p. 544), cyclu-C5H~P, 2,4,6-Ph3C5H~P; Me,P=PCF,; P73- anion(31) (isoelectronic with P4S3) in Sr3P14; PIl3- anion in Na3PII; diazaph~spholed~~) [ P ~ P { M ~ ( v ' - C)(CO)2}21'33', ~H~ [(fluorenyl)=P{=C(SiMe3)2}]-(33a) p4, PH3, p x3, p406, [ P ~ P { C O ( C O ) ~ } ~ I ( ~ ~ ) PH4+, C13P0, P4010, Pod3-, polyphosphates, MP (zinc-blende type, M = B, Al, Ga, In), [ C O ~ ( C O ) ~ ( ~ ~ - P P ~ ) ] , ( ~ ~ ) [(P4)Ni((Ph2PCH2CH2)3N}];(36) many complexes of PR3 etc., with metal centres PBr4 -, [PBr2(CN)21- .(37) [ p(q3- P3)( Ni(triphos)}~]~+(~*) PF5, PPh5 [CO~(CO)S(~-CO):!(~~-PP~)ZI,I S ( ~ C L ~ - P O M ~ ) I ( ~ ~ ) [OS~(CO) PF6-,...
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This note was uploaded on 10/12/2012 for the course CHEMISTRY CHM1040 taught by Professor Jhon during the Spring '12 term at Florida A&M.

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