Dissociation Energy of the Gaseous TlBi MoleculeG. De Maria, L. Malaspina, and V. Piacente Citation: The Journal of Chemical Physics 56, 1978 (1972); doi: 10.1063/1.1677483 View online: http://dx.doi.org/10.1063/1.1677483 View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/56/5?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Atomization energies of gaseous molecules of Li with Bi and Pb J. Chem. Phys. 76, 2687 (1982); 10.1063/1.443253 Dissociation Energy of the TlAs Molecule J. Chem. Phys. 56, 1780 (1972); 10.1063/1.1677442 Dissociation Energies of Group VIa Gaseous Homonuclear Diatomic Molecules. II. Selenium J. Chem. Phys. 48, 2867 (1968); 10.1063/1.1669544 Dissociation Energies of Group VIa Gaseous Homonuclear Diatomic Molecules. I. Sulfur J. Chem. Phys. 48, 2859 (1968); 10.1063/1.1669543 Dissociation Energy of the Gaseous AlP Molecule J. Chem. Phys. 44, 2531 (1966); 10.1063/1.1727078

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THE JOURNAL OF CHEMICAL PHYSICS VOLUME 56, NUMBER 5 1 MARCH 1972

Dissociation Energy of the Gaseous TlBi Molecule

G. DE MARIA, L. MALASPINA, AND V. PIACENTE

Laboratorio di Chimica Fisica delle Alte Temperature, /stituto di Chimica Fisica, Universita di Roma, Rome, Italy

(Received 28 July 1971)

The Knudsen cell-mass spectrometric technique has been used to identify the heteronuclear molecule TIBi. The thermodynamic treatment of the data led to a value of the dissociation energy DoO(TlBi) =

28±3 kcal mole-I. A comparison between bond energies in condensed and gaseous IIIb-Vb binary com­pounds is reported.

INTRODUCTION

Heteronuclear molecules from the Group IIIb-Vb elements have previously been investigated by mass spectrometry.1-4 A critical assessment of the relative bond energy data has shown the existence of a trend of the dimensionless parameter a= 0.5 t:Jr298(atom)/ Do ° along the series BN, AlP, InSb, and GaAs,2 where dlJ0298(atom) is the heat of atomization of the solid com­pound and Do ° the dissociation energy of the cor­responding heteronuclear gaseous molecule.

To complete this series the TlBi system was ex­amined. The identification and thermodynamic proper­ties of the gaseous molecule are reported in the present work.

EXPERIMENTAL PROCEDURE AND RESULTS

An Inghram-type, 12-in. radius curvature, 60° mag­netic sector mass spectrometer was used in the experi­ments. The general features of the method used have been described elsewhere.· Two compartments, divided

using the pressure independent equilibrium

Bi(g) + BiTI (g) +=tTl (g) + Bi2(g) (1)

and the dissociation reaction

TlBi (g) +=tTl (g) + Bi(g). (2)

Three series of experiments were carried out at 60 eV. The pressure calibration was made by quantitative silver vaporization.

The maximum ionization cross section values used were 27,631.7,730.0,744,8 and 43,8 respectively, for Ag, Bi, TI, Bi2, and TIBi.

Third-law l1lloo values for Reactions (1) and (2) are reported in Table I. The IlHo ° values for Reaction (1) were obtained directly from ion intensity measure­ments corrected by the ionization cross section. The ion intensity values of the Bi+ were corrected for the fragmentation of the diatomic species by the relation9;

by a vertical wall (0.7 mm high and 1 mm thick) were The free energy functions for Bi, TI, and Bi2 were drilled into a standard graphite Knudsen cell (1.5 em taken from JAN AF/o while for TlBi the values were deep, 1.3 em i.d.), with a knife-edge orifice 1 mm in estimated assuming the interatomic distance r.= 2.72 diam. Pure thallium and bismuth were loaded sepa- A obtained assuming there is a triple bond and taking rately in the two compartments so that interaction into account the electronegativity correction,ll the between them would occur predominantly in the gas vibration frequency w= 118 em-I, as estimated follow­phase. This procedure was found most suitable for the ing a procedure suggested by Baugham,12 and the investigation of the TlBi molecular species. In fact, electronic ground state 3~ by analogy with the isosteric with this arrangement, the reacting elements are at molecule Pb2. near unit activity, so that the formation and therefore The average third-law value of dHoo= -19.1±0.4 the identification of the heteronuclear molecule is kcal/mole is in agreement with the dHoo= -16.6±5 favored. kcaljmole obtained by the second law treatment of

The temperature was measured using aPt, Pt-Rh the Kp data of the Reaction (1) (Fig. 1). (10%) thermocouple calibrated at the melting points Combining the most probable heat of Reaction (1) of Sn and Zn. In addition to TI, Bi, and Bi2 molecules, (l1llo ° = -19±4 kcalj mole) with the literature value the TlBi species was unambiguously identified by of DoO(Bi2) =47±1 kcalj mole,9 ,13-1. the dissociation mass-to-charge ratio, appearance potential, isotopic energy of the TlBi molecule is DoO(TlBi) = 28±5 distribution, and intensity distribution in the molecular kcal/mole. beam. The appearance potential of TlBi measured by This value is in close agreement with the values the linear extrapolation method, assuming Hg as AHoo= 26.8±5.0 and AHoo= 27.8±0.3 kcaljmole for standard, was 7.5±OA eV. the dissociation Reaction (2) obtained using second

The dissociation energy of this species was evaluated and third law methods, respectively. The agreement 1978

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DISSOCIATION ENERGY OF GASEOUS TlBi 1979

TABLE I. Third-law t;.Hoo values in kilocalories per mole for reactions: (1) Bi(g) +BiTl(g)~Bi2(g) +Tl(g); (2) BiTl(g)~Bi(gHTl(g).

T PBi PBi2 PT1 PBiTI t;.[(GT o-HoO)/TJ(1) [(t;.GT o-HoO)/TJ(2) t;.Ho(1) ° t;.HO(2) ° (OK) (Atm) (Atm) (Atm) (Atm)

904 l.60XIO-s 2.40Xl(J6 2. 14XI0-6 3.40XIO-o 2.72 21.74 -18.91 27.92 917 2.32XI0-6 3.44X10-6 3.27X10-6 5.50XIO-o 2.74 21.71 -19.04 27.75 930 3.30XIO-s 4.76XIO-s 4.34XI0-6 8.70XIO-o 2.77 21.68 -18.98 27.79 941 4.20Xl(J6 5.68XIO-s 5.20XI0-6 1.35XIO-s 2.79 21.66 -18.65 28.13 952 5.58Xl(J6 7.20XIO-s 7.05XI0-6 1. 82XIO-s 2.82 21.64 -18.80 27.87 968 7.9OXl(J6 1. 04X 10-6 1.02X10-4 3.27XIO-s 2.64 21.61 -18.51 28.14 987 1. 17XI0-6 1.39XI0-6 1. 71X 10-4 5.50XIO-s 2.68 21.58 -18.75 27.85

1017 1. 42X 10-6 2.09XI0-6 3.05XlO-4 1.04XI0-7 2.96 21.53 -20.00 28.36

882 1. 04X10-s 2.08X10-s 1.57XlO-6 2.30XIO-o 2.67 21. 77 -19.04 27.89 899 1. 72XIO-s 3.23XI0-6 2.45XI0-6 4.20XIQ-9 2.70 21.74 -18.90 27.77 915 2. 56XIO-s 4. 77Xl(J6 3.61XI0-6 6.9OXIQ-9 2.74 21. 79 -19.20 27.76 922 3. 14X10-s 5.79Xl(J6 4.43 X 10-6 9.70XlO-9 2.75 21.69 -19.10 27.55 938 4.72Xl(J6 9.10Xl(J6 6.38XI0-6 1. 68X lO-s 2.79 21.66 -19.23 27.82 946 6.20Xl(J6 1.09XI0-5 8.48XI0-6 2. 22X 10-s 2.81 21.65 -19.24 27.53 975 1. 11 X 10-6 1.93XI0-5 1. 45X 10-4 5. 13XIO-s 2.87 21.60 -19.30 27.79 984 1.32XI0-6 2.36XI0-6 1.88XI0-4 6.82XIO-s 2.87 21.53 -19.44 27.66

1000 1. 76XI0-6 2. 99XI0-5 2.49XI0-4 1.03XlO-7 2.92 21.56 -19.44 27.82 1005 1.82XI0-6 2.95XI0-6 2.73XI0-4 1. 11 X 10-7 2.93 21.55 -19.44 27.86

872 8.60XI0-7 1. 62X10-s 1.30XI0-6 1. 50X 10-0 2.64 21.80 -19.13 27.51 875 9.05XI0-7 1.49Xl(J6 1. 16XI0-6 1. 42X10-D 2.65 21. 79 -18.86 27.62 895 1.34XI0-6 2.30Xl(J6 1. 68XI0-6 2.35XI0--9 2.68 21.77 -19.07 27.65 915 2.42XI0-6 4. 16XlO; 3.01X10-6 5.46X 10--9 2.74 21.70 -19.00 27.71 945 4.80X1(J6 8.48XIO-s 6.33XI0-6 1. 45X10-s 2.80 21.65 -19.48 27.72 981 1.05XI0-6 1. 73XlO-6 1. 19XI0-4 3.96XIO-s 2.88 21.59 -19.40 27.91

1015 2.21XI0-6 3. 13XlO-6 1.81 X 10-4 9.08X10-s 2.95 21.58 -18.96 28.22 1028 2.96X10-6 4. 19XI0-6 2.78XI0-4 1.38XI0-7 2.98 21.51 -19.30 27.89 1045 3.96XI0-6 5. 64X 10-5 4. 12XI0-4 2.06XI0-7 3.02 21.48 -19.70 27.70

-19.1±0.4 27.8±0.3

-3,--------------------------------------------------------------,

Ig Kp

-4

-5

-6~--------~---------L--______ ~ __________ L_ ________ ~ ________ ~

9 10 11 12

11 Tx 104 (OK-I,

FIG. 1. Second-law plot for the reaction Bi(g) + BiTI (g)->Bi2(g) +Tl(g).

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1980 DE MARIA, MALASPINA, AND PIACENTE

TABLE II. Bond energies in condensed and gaseous IIIb-Vb binary systems.

Molecule I1lJo298(atom) Doo 0.5I1Ho298(atom)

a= Doo

BN 309.1" 92.0±l1e 1.68 AlP 185.5b 50.8±3f 1.83 GaAs 158.6c 50.1±2g 1.60 InSb 128.1d 35.4±2.5" 1.82 TlBi [100J 28.0±3 i [1.8J

a Calculated combining the I1Ho ... =60 kcal/mole [P. O. Schissel and W. S. Williams, Bull. Am. Phys. Soc.4,139 (1959) J of the reaction: BN(s)---> B(.)+IN'(ol with the I1Ho, .. (cvap) (B) =136.5±0.5 kcal/mole [R. Hult· gren, R. L. Orr, and K. K. Kelley, Supplement to Selected Values of Thermo· dynamic Properlies of Metals (California U.P., 1964)J and the DoO(N,) =

225.1 kcal/mole [A. G. Gaydon, Dissociation Energies (Chapman and Hall, London, 1968) J.

b Calculated combining the I1H°,.. =127.5±3.0 kcal/mole [G. De Maria, K. A. Gingerich, and V. Piacente, J. Chern. Phys. 49, 4705 (1968) I of the reaction: AIP(s)--->AI(g)+lp,(.) with the DoO(P,) =116.1 kcal/mole [K. A. Gingerich, J. Chern. Phys. 44, 1717 (1966)J.

C Calculated combining the I1Ho29S(evap) =45.1 kcal/mole ' [W. J. Silvestri and V. J. Lyons, J. E1ectrochem. Soc. 109, 963 (1962) J of the reaction: GaAs(.) --->Ga(1)+!As'(g) with the AHo',"(evap) Ga =66.7 kcal/mole' and the DoO(As,) =91.5 kcal/mole.'

d T. Renner, Solid State Electronics I, 39 (1960). e A. G. Gaydon, Dissociation Energies (Chapman and Hall, London,

(1968) . f Reference 1. o Reference 2. h Reference 3. i This work.

shows that the equilibrium thermodynamic conditions were attained in the vapor phase even though the condensed components were separated, The most probable value of the dissociation energy of the TlBi molecule is Do 0 (TlBi) = 28±3 kcal/mole.

Thermodynamic data for the IIIb-Vb heteronuclear molecules and corresponding condensed systems are summarized in Table II. The heat of atomization of TlBi(s) ~Ho2~100 kcal/mole was evaluated from the Do 0 of the heteronuclear gaseous species determined in this work and the corresponding a= 1.8 estimated by comparison with the data obtained for the other systems,

The a value appears to be between 1.6 and 1.8, reflecting the parallel decrease of the bond energy both in the crystal and in the diatomic molecule along the IIIb-Vb series.

1 G. De Maria, K. A. Gingerich, L. Malaspina, and V. Piacente, J. Chern. Phys. 44, 2531 (1966).

2 G. De Maria, L. Malaspina, and V. Piacente, J. Chern. Phys. 52, 1019 (1970).

3 G. De Maria, J. Drowart, and M. G. Inghram, J. Chern. Phys. 31,1076 (1959).

4 K. A. Gingerich and V. Piacente, J. Chern. Phys. 54, 2498 (1971).

6 M. G. Inghram and J. Drowart, Mass Spectrometry Applied to High Temperature Chemistry in High Temperature Technology (McGraw-Hili, New York, 1960).

6 G. De Maria and V. Piacente, Bull. Soc. Chim. Belg. (to be published).

7 G. W. Otvos and D. P. Stevenson, J. Am. Chern. Soc. 78, 546 (1956).

8 (a) R. Colin, P. Goldfinger, and M. Jeunehomme, paper presented at the ASTM Conference on Mass Spectrometry, Chicago, Illinois, 4--9 June 1961; (b) R. Colin, Ind. Chim. Beige 26,51 (1961).

9 F. J. Kohl, O. Manuel, and K. D. Carlson, J. Chern. Phys. 47,2667 (1967).

10 JAN A F Thermochemical Tables (The Dow Chemical Co., Midland, Michigan, 1963).

II L. Pauling, The Nature of the Chemical Bond (Cornell Univer­sity, Ithaca, N.Y., 1960).

12 E. C. Baugham, Trans. Faraday Soc. 48,121 (1964). 13 A. T. Aldred and J. N. Pratt, Trans Faraday Soc. 59, 673

(1967). 14 J. H. Kim and A. Cosgarea, J. Chern. Phys. 44, 806 (1966). 16 A. K. Fischer, J. Chern. Phys. 45, 375 (1966).

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