Gold
Main page |
| Other names/abbreviations: | Au |
| Element no: | 79 |
| Element group: | 11 (IUPAC) I B (American labelling) I B (European labelling) Coinage metals |
| Element type: | Transition metals |
| CAS-Number: | 7440-57-5 |
| EINECS-Number: | 231-165-9 |
Chemical properties
Reaction of gold with aidsGold metal dissolves in aqua regia, a mixture of hydrochloric acid, HCl, and concentrated nitric acid, HNO3, in a 3:1 ratio.
Reaction of gold with air
Gold does not react with air under normal conditions.
Reaction of gold with bases
Gold does not react with aqueous bases.
Reaction of gold with the halogens
Gold metal reacts with chlorine, Cl2, and bromine, Br2, forming the trihalides gold(III) chloride, AuCl3, and gold(III) bromide, AuBr3, respectively.
2 Au (s) + 3 Cl2 (g)
2 AuCl3 (s)2 Au (s) + 3 Br2 (g)
2 AuBr3 (s)Gold reacts with iodine, I2, forming the monohalide gold(I) iodide, AuI.
2 Au (s) + I2 (g)
2 AuI (s)Reaction of gold with water
Gold does not react with water.
Physical properties
Appearance | ||
| Physical state @ 20°C: | Solid | |
| Color: | Gold [3] | |
| Luster: | Metallic [3] | |
| Transparency: | Opaque [3] | |
| Streak: | Yellow [3] | |
Bulk properties | ||
| Molecular weight (g/mol): | 196.96655 [1] | |
| Melting point (°C): | 1064 [1] | |
| Boiling point (°C): | 2808 [1] | |
| Density (g/cm3): | 19.32 [1] | |
| Molar volume (cm3): | 10.22 (20 °C) [2] | |
| Velocity of sound (m/s): | 1740 | |
| Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa): Poisson ratio: |
76-81 [2] 26-29 [2] 171 [2] 0.42 [2] | |
| Hardness: Mineral hardness: Brinell hardness (MN/m2): Vicker hardness (MN/m2): |
2.5-3 [3] 2450 216 | |
Optical properties | ||
| Reflectivity (%): | 95 | |
Thermodynamic properties | ||
| ΔH°atomization (kJ/mol): | 379±8 [1] | |
| ΔH°fusion (kJ/mol): | 12.8 [1] | |
| ΔH°vaporization (kJ/mol): | 343±11 [1] | |
| Cp (solid) (J/K·mol): | 24.8145 (20 °C) [2] 25.6389 (100 °C) [2] 27.9473 (500 °C) [2] 29.7610 (900 °C) [2] | |
| Coeff. of linear thermal expansion (106 K-1): | 14.2 (100 °C) [2] 15.2 (500 °C) [2] 16.7 (900 °C) [2] | |
Crystal structure | ||
| Crystal type: | Face centered cubic [2]; Isometric; 4/m bar 3 2/m | |
| Cleavage: | Absent [3] | |
| Fracture: | Jagged [3] | |
Electronic properties | ||
 |
Electron configuration: | 1s2-2s2-2p6-3s2-3p6-3d10-4s2-4p6-4d10-4f14-5s2-5p6-5d10-6s1 |
| Atomic radius (Å): | 1.79 | |
| Ionic radius (Å): | Au(I): 1.37 (6-coordinate) [1] Au(III): 0.85 (6-coordinate) [1] Au(IV): 0.57 (6-coordinate) [1] | |
Conductivity | ||
| e°(V): | 1.68 | |
| Electrical resisitvity (μΩ·cm): | 2.2 (20 °C) [2] 2.0 (25 °C) [2] 2.8 (100 °C) [2] 6.8 (500 °C) [2] 11.8 (900 °C) [2] | |
| Thermal (W/m·K): | 293 (20 °C) [2] 293 (100 °C) [2] | |
References
1: Greenwood,N.N., Earnshaw,A. Chemistry of the elements2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain
2: Buch,A. Pure Metals Properties. A Scientific-Technical Handbook
1st edition (1999) Edited by Buch,A. pp. 1-306, ASM International and Freund Publishing House Ltd. Ohio. USA
3: Korbel,P., Novák,M. The Complete Encyclopedia of Minerals
1st edition (1999) pp1-296, Chartwell Books, Inc. New Jersey, USA
© Michael Pilgaard
Created: November 14, 2006
Last update: May 5, 2008