24
Cr
Chromium
51.9961
Chromium (Cr)
Transition MetalGroup 6Period 4d-block-block
Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point.
Latin name: Chromium
Atomic Number
24
Atomic Mass
51.9961 g/mol
Phase (STP)
Solid
Electron Config.
[Ar] 3d⁵ 4s¹
General
SymbolCr
Atomic Number24
Atomic Mass51.9961 g/mol
CategoryTransition Metal
Group6
Period4
Blockd-block
Electron Configuration[Ar] 3d⁵ 4s¹
Valence Electrons6
Coloursteely-grey metallic
Appearancesilvery metallic
CAS NumberCAS7440-47-3
Physical Properties
Phase (STP)Solid
Density7.19 g/cm³
Melting Point1906.85°C · 3464.33°F · 2180.00 K
Boiling Point2670.85°C · 4839.53°F · 2944.00 K
Atomic Properties
Atomic Radius166 pm
Electronegativity1.66 Pauling
Ionization Energy653 kJ/mol
Oxidation States+6, +3, +2
Ion ChargeCr2+/Cr3+/Cr6+
Thermodynamic
Molar Heat23.35 J/(mol·K)
Crystal Structure
Crystal Structurebody-centered cubic
Mechanical Properties
Mohs Hardness8.5
Abundance
In Earth's Crust0.0110%
Discovery & History
Discovery Year1797
Discovered ByLouis-Nicolas Vauquelin
Country of DiscoveryFrance
Isotopes of Chromium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Cr-50 | 4.345% | Stable | — |
| Cr-52 | 83.789% | Stable | — |
| Cr-53 | 9.501% | Stable | — |
| Cr-54 | 2.365% | Stable | — |