WebElements

Periodic Table

chromium

Atomic number: 24
Atomic weight: 51.9961
Symbol: Cr
Group number: 6
Electronic configuration: [Ar].3d5.4s1

Description

Chromium is steel-gray, lustrous, hard, metallic, and takes a high polish. Its compounds are toxic. It is found as chromite ore. Siberian red lead is a chromium ore prized as a red pigment for oil paints.

General information

Discoveror: Louis-Nicholas Vauquelin
Date discovered: 1797
Discovered at: France
Meaning of name: From the Greek word "chroma" meaning "colour"

Physical data

Standard state: solid at 298 K
Colour: silvery metallic
Density of solid at ambient temperature/kg m-3: 7140
Molar volume/cm3: 7.23

Radii /pm

Atomic: 166
Covalent (single bond):
Pauling radius for the ion [Cr]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius162.6no data45.5no data

Electronegativities

Both values are quoted on the Pauling scale.

Pauling: 1.66
Allred Rochow: 1.56

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: 2180
boiling point: 2944

Enthalpies /kJ mol-1

fusion: 20.5
vaporization: 350

single bond enthalpies:
Cr-F Cr-Cl Cr-Br Cr-I Cr-Cr
no data no data no data no data 155

Ionization enthalpies /kJ mol-1

Number Enthalpy
1st652.8
2nd1496
3rd2987
4th4740
5th6690
6th8738
7th15550
8th17820

Isotopes

This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
50Cr49.9460464 (17)4.345 (9)
52Cr51.9405098 (17)83.789 (12)
53Cr52.9406513 (17)9.501 (11)
54Cr53.9388825 (17)2.365 (5)

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/Cr.html