Molybdenum
Main page |
| Other names/abbreviations: | Mn |
| Element no: | 42 |
| Element group: | 6 (IUPAC) VI B (American labelling) VI A (European labelling) |
| Element type: | Transition metals |
| CAS-Number: | 7439-98-7 |
| EINECS-Number: | 231-107-2 |
Chemical properties
Reaction of molybdenum with acidsMo(VI) is reduced to Mo(IV) by ascorbic acid. The reaction is fast [3].
Reaction of molybdenum with glycols
Mo(VI) is reduced to Mo(IV) by glycols [3].
| Glycols | Reductive coefficient (x 10-7 M-1·s-1) | |
| Ethylene glycol Diethylene glycol Triethylene glycol Tetraethylene glycol PEG |
1.06 22.5 2.25 1.80 2.55 | |
| Reductive coefficients for glycols adapted from [3]. | ||
Reaction of molybdenum with nucleotides
Mo(VI) is reduced to Mo(IV) by L-cysteine. Reductive coefficient = 1.26·10-4 M-1·s-1 [3]
Reaction of molybdenum with sulfide
Mo(VI) is precipitated by sulfide in 0.4 M hydrochloric acid
MoO42- (aq) + 3 S2- (aq) + 8 H+ (aq)
MoS3 (s) [brown/black] + 4 H2O (l)The precipitate can be dissolved by sodium disulfide
2 MoS3 (s) + S22- (aq)
2 MoS42- (aq)Mo(VI) as ammonium molybdate is precipitated by hydrogen sulfide in the presence of ammonia:
MoO42- (aq) + 4 H2S (aq) + 2 NH4+ (aq)
(NH4)2MoS4 (s) [red] + 4 H2O(l)Quantitative analysis
Method 3500-Mo C Inductively Coupled Plasma Method [7]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.Method limit of detection in water = 0.002 mg/L
Method limit of detection in soil = 1.00 mg/kg
Safety
Symbol: -R-phrases: -
S-phrases: -
Physical properties
Appearance | ||
| Physical state @ 20°C: | Solid [5] | Color: | Gray [5] | Odor: | Odourless [5] |
Bulk properties | ||
| Molecular weight (g/mol): | 95.94(1) [1] | |
| Melting point (°C): | 1620 [1] | |
| Boiling point (°C): | 4650 [1] | |
| Density (g/cm3): | 10.28 [1] | |
| Molar volume (cm3): | 9.41 (20°C) [4] | |
| Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa): Poisson ratio: |
323-336 [4] 122 [4] 299 [4] 0.32-0.34 [4] | |
Thermodynamic properties | ||
| ΔfH°gas (kJ/mol): | 664±13 (Monoatomic) [1] 658.1 [6] | |
| ΔfH°solid (kJ/mol): | 0.0 [6] | |
| ΔH°fusion (kJ/mol): | 37.48 [6] | |
| ΔH°vaporization (kJ/mol): | 590±20 [1] | |
| S°gas (J/K·mol): | 182.0 [6] | |
| S°solid (J/K·mol): | 28.7 [6] | |
| ΔfG°gas (kJ/mol): | 612.5 [6] | |
| Cp (gas) (J/K·mol): | 20.8 (25 °C) [6] | |
| Cp (solid) (J/K·mol): | 23.5714 (20 °C) [4] 24.06 (25 °C) [6] 24.8162 (100 °C) [4] 27.1854 (500 °C) [4] 29.5947 (1000 °C) [4] 32.3655 (1500 °C) [4] | |
| Coeff. of linear thermal expansion (106 K-1): | 5.1 (20 °C) [4] 4.8 (25 °C) [6] 5.2 (100 °C) [4] 5.7 (500 °C) [4] 5.75 (1000 °C) [4] 6.51 (1500 °C) [4] | |
Crystal structure | ||
| Crystal type: | Body centered cubic [4] | |
Electronic properties | ||
 |
Electron configuration: | 1s2-2s2-2p6-3s2-3p6-3d10-4s2-4p6-4d5-5s1 |
| Ionic radius (Å): | Mo(VI): 0.59 (6-coordinate) [1] Mo(V): 0.61(6-coordinate) [1] Mo(IV): 0.65 (6-coordinate) [1] Mo(III): 0.69 (6-coordinate) [1] | |
Conductivity | ||
| Electrical resisitvity (μΩ·cm): | 5.70 (20 °C) [4] 5.30 (25 °C) [4] 7.6 (100 °C) [4] 17.6 (500 °C) [4] 31 (1000 °C) [4] 46 (1500 °C) [4] | |
| Thermal (W/m·K): | 142 (20 °C) [4] 138 (27 °C) [6] 138 (100 °C) [4] 121 (500 °C) [4] 105 (1000 °C) [4] 84 (1500 °C) [4] | |
History
DiscoveryMolybdenum discovered in by 1778 Carl Welhelm Scheele while working with the mineral as molybdenite. Molybdenum metal was prepared in an impure form in 1782 by Peter Jacob Hjelm [6].
Origin of name
From the Greek word "molybdos" meaning "lead". Molybdenite was mistakenly taken for a lead and graphite ore [6].
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: Mukhopadhyay,A., Karkamkar,A., Kolehmainen,E., Rao,C.P. Transition metal-saccharide chemistry: synthesis, characterization and solution stability studies of cis-dioxomolybdenum saccharide complexes
Carbohydr. Res. (1998) 311 (3) 147-154
3: Bandwar,R.P., Rao,C.P. Relative reducing abilities in vitro of some hydroxy-containing compounds, including monosaccharides, towards vanadium(V) and molubdenum(VI)
Carbohydr. Res. (1995) 277 197-207
4: 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
5: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5
6: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA
7: Standard Methods for the Analysis of Water and Wastewater, APHA, 1992, 18th edition
© Michael Pilgaard
Created: October 3, 2008
Last update: October 13, 2008