Chromium

24
Cr
Group
6
Period
4
Block
d
Protons
Electrons
Neutrons
24
24
28
General Properties
Atomic Number
24
Atomic Weight
51.9961
Mass Number
52
Category
Transition metals
Color
Silver
Radioactive
No
From the Greek word chroma, color
Crystal Structure
Body Centered Cubic
History
In 1797, Louis Nicolas Vauquelin received samples of crocoite ore.

In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven, making him the discoverer of the element.

Vauquelin was also able to detect traces of chromium in precious gemstones, such as ruby or emerald.
Electrons per shell
2, 8, 13, 1
Electron Configuration
[Ar] 3d5 4s1
Cr
Chromium oxide was used by the Chinese in the Qin dynasty over 2,000 years ago
Physical Properties
Phase
Solid
Density
7.15 g/cm3
Melting Point
2180.15 K | 1907 °C | 3464.6 °F
Boiling Point
2944.15 K | 2671 °C | 4839.8 °F
Heat of Fusion
20.5 kJ/mol
Heat of Vaporization
339 kJ/mol
Specific Heat Capacity
0.449 J/g·K
Abundance in Earth's crust
0.014%
Abundance in Universe
0.0015%
High
Image Credits: Wikimedia Commons (Alchemist-hp)
High purity chromium crystals, produced by chemical transport reaction through decomposition of chromium iodides, as well as a high purity chromium cube for comparison
CAS Number
7440-47-3
PubChem CID Number
23976
Atomic Properties
Atomic Radius
128 pm
Covalent Radius
139 pm
Electronegativity
1.66 (Pauling scale)
Ionization Potential
6.7665 eV
Atomic Volume
7.23 cm3/mol
Thermal Conductivity
0.937 W/cm·K
Oxidation States
-2, -1, 1, 2, 3, 4, 5, 6
Applications
Chromium is used to harden steel, manufacture stainless steel, and form many useful alloys.

It is mostly used in plating to produce a hard, beautiful surface and to prevent corrosion.

The metal is also widely used as a catalyst.

Chromium compounds are valued as pigments for their vivid green, yellow, red and orange colors.
In larger amounts, chromium can be toxic and carcinogenic
Isotopes
Stable Isotopes
50Cr, 52Cr, 53Cr, 54Cr
Unstable Isotopes
42Cr, 43Cr, 44Cr, 45Cr, 46Cr, 47Cr, 48Cr, 49Cr, 51Cr, 55Cr, 56Cr, 57Cr, 58Cr, 59Cr, 60Cr, 61Cr, 62Cr, 63Cr, 64Cr, 65Cr, 66Cr, 67Cr