Chromium

Chromium (Cr)

Hard silvery transition element. Used in decorative electroplating. Discovered in 1797 by Vauquelin.
Atomic Number24
Atomic Weight51.9961
Mass Number52
Group6
Period4
Blockd
Protons24 p+
Neutrons28 n0
Electrons24 e-
Chromium crystals and 1cm3 cube.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram

Properties

Atomic Radius
140 pm
Atomic Volume
Covalent Radius
122 pm
Metallic Radius
119 pm
Ionic Radius
73 pm
Crystal Radius
87 pm
Van der Waals radius
206 pm
Density
7.15 g/cm³
Boiling Point
2,945 K
Melting Point
2,130 K
Electrons per shell2, 8, 13, 1
Electronegativity
1.66
Electrophilicity
1.1319177597467 eV/particle
Proton Affinity
791.3 kJ/mol
Electron Affinity
Ionization Potential
6.76651 eV/particle
Heat of Vaporization
342 kJ/mol
Heat of Fusion
Heat of Formation
397.48 kJ/mol
Molar Heat Capacity
23.35 J/(mol K)
Specific Heat Capacity
0.449 J/(g⋅K)
Thermal Conductivity
93.9 W/(m K)
Gas Basicity
768.4 kJ/mol
Dipole Polarizability
83 a₀
C6 Dispersion Coefficient
602 a₀
Oxidation States-2, -1, 1, 2, 3, 4, 5, 6
Color
Silver
Crystal StructureBody Centered Cubic (BCC)
Lattice Constant
2.88 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Ar] 3d5 4s1
Magnetic Ordering
Magnetic Susceptibility
PhaseSolid
Poisson Ratio
Shear Modulus
Young's Modulus
Allotropes
Alternate Names
Adiabatic Index
Appearance
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Electrical
Hardness
Magnetic Susceptibility
Magnetic
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
Classification
CategoryTransition metals, Transition metals
CAS GroupVIA
IUPAC GroupVIB
Glawe Number55
Mendeleev Number51
Pettifor Number57
Geochemical Classfirst series transition metal
Goldschmidt Classlitophile
Radioactivity
RadioactiveNo
Decay Mode
Half-Life
Lifetime
Abundance
Abundance in Earth's crust
102 mg/kg
Abundance in Oceans
0.0003 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe0.0015%

Isotopes of Chromium

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

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. From the Greek word chroma, color

DiscoverersLouis Vauquelin
Discovery LocationFrance
Discovery Year1797
Name OriginGreek: chrôma (color).
In larger amounts, chromium can be toxic and carcinogenic
Chromium oxide was used by the Chinese in the Qin dynasty over 2,000 years ago

Uses

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. Used to make stainless steel. It gives the color to rubies and emeralds. Iron-nickel-chromium alloys in various percentages yield an incredible variety of the most important metals in modern technology.

Sources

Chromite [Fe,Mg(CrO4)] is its most important mineral. Produced commercially by heating its ore in the presence of silicon or aluminium.