|Boiling Point: 3143°K, 2870°C, 5198°F
Melting Point: 1768°K, 1495°C, 2723°F
Electrons Energy Level: 2, 8, 15, 2
Isotopes: 26 + 1 Stable
Heat of Vaporization: 376.5 kJ/mol
Heat of Fusion: 16.19 kJ/mol
Density: 8.9 g/cm3 @ 300°K
Specific Heat: 0.42 J/g°K
Atomic Radius: 1.67Å
Ionic Radius: 0.745Å
Electronegativity: 1.88 (Pauling); 1.7 (Allrod Rochow)
Vapor Pressure: 175 Pa @ 1495°C
1s2 2s2p6 3s2p6d7 4s2
Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes, and ceramics. Cobalt has been detected in Egyptian sculpture and Persian jewelry from the third millennium BC, in the ruins of Pompeii (destroyed AD 79), and in China dating from the Tang dynasty (AD 618907) and the Ming dynasty (AD 13681644). Cobalt glass ingots have been recovered from shipwrecks dating to the time of the Minoans.
Alchemical Symbol, Cobalt
Swedish chemist Georg Brandt (16941768) is credited with isolating cobalt sometime between 1730 and 1737. He was able to show that cobalt was the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt.
During the 19th century, cobalt blue was produced at the Norwegian Blaafarvevaerket (70-80 % of world production), led by the Prussian industrialist Benjamin Wegner.
In 1938, John Livingood and Glenn Seaaborg discovered cobalt-60.
The word cobalt is derived from the German kobalt, from kobold meaning "goblin", a term used for the ore of cobalt by miners, who thought it worthless and who found that it was poisonous and that it polluted and degraded other mined elements, mainly due to the arsenic and sulfur also found in the ore.
Cobalt's primary ores are cobaltite (CoAsS) and erythrite (Co3(AsO4)2).
Cobalt is ferromagnetic with atomic number 27. The Curie temperature is of 1388oK with 1.6~1.7 Bohr magnetons per atom. It is frequently associated with nickel, and both are characteristic ingredients of meteoric iron. Mammals require small amounts of cobalt salts. Cobalt-60, an artificially produced radioactive isotope of cobalt, is an important radioactive tracer and cancer treatment agent. Cobalt has a relatively permeability two thirds that of iron. Metallic cobalt commonly presents a mixture of two crystallographic structure.
Common oxidation states of cobalt include +2 and +3, though +1 is also seen.
Cobalt is not found as a free-metal and is generally found in the form of ores. Cobalt is usually not mined alone, and tends to be produced as a by-product of nickel and copper mining activities. The main ores of cobalt are cobaltite, erythrite, glaucodot, and skutterudite. The world's major producers of cobalt are the Democratic Republic of the Congo, the People's Republic of China, Zaambia, Russia and Australia. It is also found in Finland, Azerbaijan, Kazakhstan and Morocco. It is also produced in the mines of Cobalt, Ontario, Canada as a byproduct of silver mining.
Use in Medicine
Cobalt-60 or 60Co is a radioactive metal that is used in radiotherapy. It produces two gamma rays with energies of 1.17 MeV and 1.33 MeV. The 60Co source is about 2 cm in diameter and as a result produces a geometric penumbra, making the edge of the radiation field fuzzy. The metal has the unfortunate habit of producing a fine dust, causing problems with radiation protection. The 60Co source is useful for about 5 years but even after this point is still very radioactive, and so cobalt machines have fallen from favor in the Western world where linacs are common. Cobalt with alloying additions of chromium and molybdenum is widely used as a bio-medical implant material.
Co-60 is useful as a gamma ray source partially because it can be produced - in known quantity, and very large amounts - by simply exposing natural cobalt to neutrons in a reactor for a given time.
Cobalt in small amounts is essential to many living organisms, including humans. Having 0.13 to 0.30 mg/kg of cobalt in soils markedly improves the health of grazing animals. Cobalt is a central component of the vitamin cobalamin, or vitamin B12.
There is a wide variety of cobalt compounds. The +2 and +3 oxidation states are most prevalent, however cobalt (I) complexes are also fairly common. Cobalt (II) salts form the red-pink [Co(OH2)6]2+ complex in aqueous solution. Adding excess chloride will also change the colour from pink to blue, due to the formation of [CoCl4]2-. Cobalt oxides are antiferromagnetic at low temperature: CoO (Neel temperature 291oK) and Co3O4 (Neel temperature: 40oK).
Naturally occurring cobalt is composed of 1 stable isotope, 59Co. 26 radioisotopes have been characterized with the most stable being 60Co with a half-life of 5.2713 years, 57Co with a half-life of 271.74 days, 56Co with a half-life of 77.233 days, and 58Co with a half-life of 70.86 days. All of the remaining radioactive isotopes have half-lives that are less than 18 hours and the majority of these have half-lives that are less than 1 second. This element also has 4 meta states, all of which have half-lives less than 15 minutes.
The isotopes of cobalt range in atomic weight from 47 amu (47Co) to 75 amu (75Co). The primary decay mode before the most abundant stable isotope, 59Co, is electron capture and the primary mode after is beta decay. The primary decay products before 59Co are element 26 (iron) isotopes and the primary products after are element 28 (nickel) isotopes.
|Powdered cobalt in metal form is a fire hazard. Cobalt compounds should be handled with care due to cobalt's slight toxicity.|
Ingestion of 60Co will lead to incorporation of some cobalt into tissues, which is released very slowly.
|60Co is a powerful gamma ray emitter and exposure to it is therefore a cancer risk.|
60Co is a risk factor in a nuclear confrontation because neutron emissions will convert 59Co into this isotope. Some nuclear wepaons designs could intentionally increase the amount of 60Co dispersed as nuclear fallout this is sometimes called a dirty bomb or cobalt bomb, once predicted by a leading scientist as being capable of wiping out all life on earth. The risk in the absence of a nuclear war comes from improper handling (or theft) of medical radiotherapeutic units. Nevertheless, the gamma radiation emitted from 60Co is used to kill bacteria on fruit and vegetables thus increasing their shelf life. This process is referred to as irradiation.
|Ionization Energy (eV): 7.881 eV
Estimated Crustal Abundance: 2.5×101 milligrams per kilogram
Estimated Oceanic Abundance: 2×10-5 milligrams per liter