WebElements

Periodic Table

molybdenum

Atomic number: 42
Atomic weight: 95.94
Symbol: Mo
Group number: 6
Electronic configuration: [Kr].4d5.5s1

Description

Molybdenum is a silvery-white, hard, transition metal. Scheele discovered it in 1778. It was often confused with graphite and lead ore. Molybdenum is used in alloys, electrodes and catalysts. The World War 2 German artillery piece called "Big Bertha" contains molybdenum as an essential component of its steel.

General information

Discoveror: Carl William Scheele
Date discovered: 1781
Discovered at: Sweden
Meaning of name: From the Greek word "molybdos" meaning "lead"

Physical data

Standard state: solid at 298 K
Colour: grey metallic
Density of solid at ambient temperature/kg m-3: 10280
Molar volume/cm3: 9.38

Radii /pm

Atomic: 190
Covalent (single bond):
Pauling radius for the ion [Mo]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius175.3no data72.9no data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 2.2
Allred Rochow: 1.30

Crystal Structure

structure: bcc (body-centred cubic)

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.

ball-and-stick.gif

Temperatures (/K)

melting point: 2896
boiling point: 4912

Enthalpies /kJ mol-1

fusion: 36.0
vaporization: 603

single bond enthalpies:
Mo-F Mo-Cl Mo-Br Mo-I Mo-Mo
no data no data no data no data 406

Ionization enthalpies /kJ mol-1

Number Enthalpy
1st685.0
2nd1558
3rd2621
4th4480
5th5900
6th6560
7th12230
8th14800

Isotopes

This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
92Mo91.906809 (4)14.84 (4)
94Mo93.9050853 (26)9.25 (3)
95Mo94.9058411 (22)15.92 (5)
96Mo95.9046785 (22)16.68 (5)
97Mo96.9060205 (22)9.55 (3)
98Mo97.9054073 (22)24.13 (7)
100Mo99.907477 (6)9.63 (3)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/Mo.html