RHODIUM

Introduction

Atomic Number: 45
Group: 9 or VIII B
Atomic Weight: 102.9055
Period: 5
CAS Number: 7440-16-6

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

Wollaston discovered rhodium in 1803-4 in crude platinum ore he presumably obtained from South America. Rhodium occurs native withother platinum metals in river sands of the Urals and in North and South America. It is also found with other platinum metals in the copper-nickel sulfideores of the Sudbury, Ontario region. Although the quantity occurring here is very small, the large tonnages of nickel processed make the recoverycommercially feasible. The annual world production of rhodium is only 7 or 8 tons. The metal is silvery white and at red heat slowly changes in airto the sesquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. Itsmajor use is as an alloying agent to harden platinum and palladium. Such alloys are used for furnace windings, thermocouple elements, bushings forglass fiber production, electrodes for aircraft spark plugs, and laboratory crucibles. It is useful as an electrical contact material as it has a low electricalresistance, a low and stable contact resistance, and is highly resistant to corrosion. Plated rhodium, produced by electroplating or evaporation, isexceptionally hard and is used for optical instruments. It has a high reflectance and is hard and durable. Rhodium is also used for jewelry, for decoration,and as a catalyst. Forty four isotopes and isomers are now known. Soluble salts should not exceed 0.01 mg/m^3. Rhodium metal (powder) costs about$300/g (99.9% pure). 1

• "An exceedingly thin coating of rhodium is used to give rhodium finish, a warm satiny luster, feebly pink, to jewelry." 2

Physical Properties

Melting Point:3*  1964 °C = 2237.15 K = 3567.2 °F
Boiling Point:3* 3695 °C = 3968.15 K = 6683 °F
Sublimation Point:3 
Triple Point:3 
Critical Point:3 
Density:4  12.4 g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration:  *[Kr] 5s1 4d8
Block: d
Highest Occupied Energy Level: 5
Valence Electrons: 

Quantum Numbers:

n = 4
ℓ = 2
m = 0
ms = -½

Bonding

Electronegativity (Pauling scale):5 2.28
Electropositivity (Pauling scale): 1.72
Electron Affinity:6 1.137 eV
Oxidation States: +3,4,6
Work Function:7 4.98 eV = 7.97796E-19 J

Ionization Potential   eV 8  kJ/mol  
1 7.4589    719.7
Ionization Potential   eV 8  kJ/mol  
2 18.08    1744.5
Ionization Potential   eV 8  kJ/mol  
3 31.06    2996.8

Thermochemistry

Specific Heat: 0.243 J/g°C 9 = 25.006 J/mol°C = 0.058 cal/g°C = 5.977 cal/mol°C
Thermal Conductivity: 150 (W/m)/K, 27°C 10
Heat of Fusion: 21.5 kJ/mol 11 = 208.9 J/g
Heat of Vaporization: 493 kJ/mol 12 = 4790.8 J/g
State of Matter Enthalpy of Formation (ΔHf°)13 Entropy (S°)13 Gibbs Free Energy (ΔGf°)13
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 7.56 31.63104 0 0
(g) 133.1 556.8904 44.383 185.698472 122.1 510.8664

Isotopes

Nuclide Mass 14 Half-Life 14 Nuclear Spin 14 Binding Energy
100Rh 99.908122(20) 20.8(1) h 1- 857.62 MeV
101Rh 100.906164(18) 3.3(3) a 1/2- 873.15 MeV
102Rh 101.906843(5) 207.0(15) d (1-,2-) 881.22 MeV
103Rh 102.905504(3) STABLE 1/2- 889.29 MeV
104Rh 103.906656(3) 42.3(4) s 1+ 897.36 MeV
105Rh 104.905694(4) 35.36(6) h 7/2+ 905.43 MeV
106Rh 105.907287(8) 29.80(8) s 1+ 913.50 MeV
107Rh 106.906748(13) 21.7(4) min 7/2+ 921.57 MeV
108Rh 107.90873(11) 16.8(5) s 1+ 929.64 MeV
109Rh 108.908737(13) 80(2) s 7/2+ 937.72 MeV
110Rh 109.91114(5) 28.5(15) s (>3)(+#) 936.47 MeV
111Rh 110.91159(3) 11(1) s (7/2+) 944.54 MeV
112Rh 111.91439(6) 3.45(37) s 1+ 952.62 MeV
113Rh 112.91553(5) 2.80(12) s (7/2+) 960.69 MeV
114Rh 113.91881(12) 1.85(5) s 1+ 968.76 MeV
115Rh 114.92033(9) 0.99(5) s (7/2+)# 967.51 MeV
116Rh 115.92406(15) 0.68(6) s 1+ 975.59 MeV
117Rh 116.92598(54)# 0.44(4) s (7/2+)# 983.66 MeV
118Rh 117.93007(54)# 310(30) ms (4-10)(+#) 982.41 MeV
119Rh 118.93211(64)# 300# ms [>300 ns] 7/2+# 990.48 MeV
120Rh 119.93641(64)# 200# ms [>300 ns] 998.56 MeV
121Rh 120.93872(97)# 100# ms [>300 ns] 7/2+# 1,006.63 MeV
122Rh 121.94321(75)# 50# ms [>300 ns] 1,005.38 MeV
89Rh 88.94884(48)# 10# ms [>1.5 μs] 7/2+# 731.58 MeV
90Rh 89.94287(54)# 15(7) ms [12(+9-4) ms] 0+# 745.24 MeV
91Rh 90.93655(43)# 1.74(14) s 7/2+# 758.90 MeV
92Rh 91.93198(43)# 4.3(13) s (6+) 771.63 MeV
93Rh 92.92574(43)# 11.9(7) s 9/2+# 785.29 MeV
94Rh 93.92170(48)# 70.6(6) s (2+,4+) 797.08 MeV
95Rh 94.91590(16) 5.02(10) min (9/2)+ 810.75 MeV
96Rh 95.914461(14) 9.90(10) min (6+) 819.75 MeV
97Rh 96.91134(4) 30.7(6) min 9/2+ 830.61 MeV
98Rh 97.910708(13) 8.72(12) min (2)+ 839.62 MeV
99Rh 98.908132(8) 16.1(2) d 1/2- 849.55 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. 14

Abundance

Earth -  Crust:  0.001 mg/kg = 0.0000001% 15
Earth -  Total:  252 ppb 16
Mercury -  Total:  194 ppb 16
Venus -  Total:  265 ppb 16
Chondrites - Total: 0.25 (relative to 106 atoms of Si) 17

Compounds

Safety Information


Material Safety Data Sheet - ACI Alloys, Inc.

For More Information

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:26.
(2) - Brownlee, Raymond B., Fuller, Robert W., and Whitsit, Jesse E. Elements of Chemistry; Allyn and Bacon: Boston, Massachusetts, 1959; p 545.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(5) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(7) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(13) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(14) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(15) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(16) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(17) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.