TECHNETIUM

Introduction

Atomic Number: 43
Group: 7 or VII B
Atomic Weight: 98
Period: 5
CAS Number: 7440-26-8

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)

Description • Uses/Function

Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was found in a sample of molybdenum, which was bombarded by deuterons in the Berkeley cyclotron, and which E. Lawrence sent to these investigators. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial materials have been made without success. If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars. Thirty one isotopes and isomers of technetium, with atomic masses ranging from 86 to 113, are known. 97Tc has a half-life of 2.6 X 10^6 years. 98Tc has a half-life of 4.2 X 10^6 years. The isomeric isotope 95mTc, with a half-life of 61 days, is useful for tracer work, as it produces energetic gamma rays. Technetium metal has been produced in kilogram quantities. The metal was first prepared by passing hydrogen gas at 1100°C over Tc2S7. It is now conveniently prepared by the reduction of ammonium pertechnetate with hydrogen. Technetium is a silvery-gray metal that tarnishes slowly in moist air. Until 1960, technetium was available only in small amounts and the price was as high as $2800/g. It is now commercially available to holders of O.R.N.L. permits at a price of $74/g plus packing charges. The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and conc. sulfuric acid, but is not soluble in hydrochloric acid of any strength. The element is a remarkable corrosion inhibitor for steel. It is reported that mild carbon steels may be effectively protected by as little as 55 ppm of KTcO4 in aerated distilled water at temperatures up to 250°C. This corrosion protection is limited to closed systems, since technetium is radioactive and must be confined. 99Tc has a specific activity of 6.2 X 10^8 Bq/g. Activity of this level must not be allowed to spread. 99Tc is a contamination hazard and should be handled in a glove box. The metal is an excellent superconductor at 11 K and below. 1

Physical Properties

Melting Point:2*  2157 °C = 2430.15 K = 3914.6 °F
Boiling Point:2* 4265 °C = 4538.15 K = 7709 °F
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:3  11 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration: [Kr] 5s2 4d5
Block: d
Highest Occupied Energy Level: 5
Valence Electrons: 

Quantum Numbers:

n = 4
ℓ = 2
m = 2
ms = +½

Bonding

Electronegativity (Pauling scale):4 2.10
Electropositivity (Pauling scale): 1.9
Electron Affinity:5 0.55 eV
Oxidation States: +7,4,6

Ionization Potential   eV 6  kJ/mol  
1 7.28    702.4
Ionization Potential   eV 6  kJ/mol  
2 15.26    1472.4
Ionization Potential   eV 6  kJ/mol  
3 29.54    2850.2

Thermochemistry

Specific Heat: 
Thermal Conductivity: 50.6 (W/m)/K, 27°C 7
Heat of Fusion: 24 kJ/mol 8 = 244.9 J/g
Heat of Vaporization: 660 kJ/mol 9 = 6734.7 J/g
State of Matter Enthalpy of Formation (ΔHf°)10 Entropy (S°)10 Gibbs Free Energy (ΔGf°)10
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 8.00 33.472 0 0

Isotopes

Nuclide Mass 11 Half-Life 11 Nuclear Spin 11 Binding Energy
100Tc 99.9076578(24) 15.8(1) s 1+ 860.12 MeV
101Tc 100.907315(26) 14.22(1) min 9/2+ 874.71 MeV
102Tc 101.909215(10) 5.28(15) s 1+ 882.78 MeV
103Tc 102.909181(11) 54.2(8) s 5/2+ 890.85 MeV
104Tc 103.91145(5) 18.3(3) min (3+)# 889.61 MeV
105Tc 104.91166(6) 7.6(1) min (3/2-) 897.68 MeV
106Tc 105.914358(14) 35.6(6) s (1,2) 905.75 MeV
107Tc 106.91508(16) 21.2(2) s (3/2-) 913.82 MeV
108Tc 107.91846(14) 5.17(7) s (2)+ 921.89 MeV
109Tc 108.91998(10) 860(40) ms 3/2-# 929.97 MeV
110Tc 109.92382(8) 0.92(3) s (2+) 928.72 MeV
111Tc 110.92569(12) 290(20) ms 3/2-# 936.79 MeV
112Tc 111.92915(13) 290(20) ms 2+# 944.86 MeV
113Tc 112.93159(32)# 170(20) ms 3/2-# 943.62 MeV
114Tc 113.93588(64)# 150(30) ms 2+# 951.69 MeV
115Tc 114.93869(75)# 100# ms [>300 ns] 3/2-# 959.76 MeV
116Tc 115.94337(75)# 90# ms [>300 ns] 2+# 958.52 MeV
117Tc 116.94648(75)# 40# ms [>300 ns] 3/2-# 966.59 MeV
118Tc 117.95148(97)# 30# ms [>300 ns] 2+# 965.35 MeV
85Tc 84.94883(43)# <110 ns 1/2-# 700.86 MeV
86Tc 85.94288(32)# 55(6) ms (0+) 714.52 MeV
87Tc 86.93653(32)# 2.18(16) s 1/2-# 728.18 MeV
88Tc 87.93268(22)# 5.8(2) s (2,3) 739.98 MeV
89Tc 88.92717(22)# 12.8(9) s (9/2+) 752.70 MeV
90Tc 89.92356(26) 8.7(2) s 1+ 764.50 MeV
91Tc 90.91843(22) 3.14(2) min (9/2)+ 777.23 MeV
92Tc 91.915260(28) 4.25(15) min (8)+ 788.10 MeV
93Tc 92.910249(4) 2.75(5) h 9/2+ 800.82 MeV
94Tc 93.909657(5) 293(1) min 7+ 809.83 MeV
95Tc 94.907657(6) 20.0(1) h 9/2+ 819.76 MeV
96Tc 95.907871(6) 4.28(7) d 7+ 827.83 MeV
97Tc 96.906365(5) 2.6E+6 a 9/2+ 836.84 MeV
98Tc 97.907216(4) 4.2(3)E+6 a (6)+ 843.98 MeV
99Tc 98.9062547(21) 2.111(12)E+5 a 9/2+ 852.98 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 11

Abundance

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Magazines:
(1) Raloff, Janet. Desperately Seeking Moly. Science News, September 26, 2009, pp 16-20.

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:30-4:31.
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(10) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(11) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).