Chromium (Cr)
Hard silvery transition element. Used in decorative electroplating. Discovered in 1797 by Vauquelin.
| Atomic Number | 24 |
|---|---|
| Atomic Weight | 51.9961 |
| Mass Number | 52 |
| Group | 6 |
|---|---|
| Period | 4 |
| Block | d |
| Protons | 24 p+ |
|---|---|
| Neutrons | 28 n0 |
| Electrons | 24 e- |
Properties
| Atomic Radius | 140 pm
|
|---|---|
| Atomic Volume | 7.23 cm³/mol
|
| 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 shell | 2, 8, 13, 1 |
| Electronegativity |
1.66
|
| Electrophilicity | 1.1319177597467 eV/particle
|
| Proton Affinity | 791.3 kJ/mol
|
| Electron Affinity | 0.666 eV/particle
|
| Ionization Potential | 6.76651 eV/particle
|
| Heat of Vaporization | 342 kJ/mol
|
| Heat of Fusion | 21 kJ/mol
|
| 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 Structure | Body Centered Cubic (BCC) |
| Lattice Constant | 2.88 Å
|
| Bulk Modulus | |
| Electrical Resistivity | |
| Electron Configuration | [Ar] 3d5 4s1 |
| Magnetic Ordering | |
| Magnetic Susceptibility | |
| Phase | Solid |
| 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 | |
| Category | Transition metals, Transition metals |
| CAS Group | VIA |
| IUPAC Group | VIB |
| Glawe Number | 55 |
| Mendeleev Number | 51 |
| Pettifor Number | 57 |
| Geochemical Class | first series transition metal |
| Goldschmidt Class | litophile |
| Radioactivity | |
| Radioactive | No |
| 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 Universe | 0.0015% |
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
| Discoverers | Louis Vauquelin |
|---|---|
| Discovery Location | France |
| Discovery Year | 1797 |
| Name Origin | Greek: 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.