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Cobalt

What is Cobalt

Cobalt (pronunciation: KO-bolt) is a hard, lustrous silvery-blue element belonging to the group of transition metals, and it is represented by the chemical symbol Co [1, 2, 3]. It is chemically active and can form many compounds [4]. It is a ferromagnetic metal that can be magnetized and is alloyed with nickel and aluminum to produce powerful magnets [1, 4].

Isotopes

It has one stable, naturally occurring isotope, 59Co and 28 radioisotopes out of which the most stable are 60Co, 57Co, 56Co, and 58Co with half-lives of 5.2714 years, 271.8 days, 77.27 days, and 70.86 days respectively [5]. The half-life periods of its other radioisotopes are less than 18 hours [5].

Cobalt

Where is Cobalt Found

Cobalt naturally occurs in combination with other elements in the mineral ores like cobaltite (a sulfide containing cobalt, arsenic, iron, and nickel), erythrite (hydrated cobalt arsenate), and skutterudite (cobalt arsenate) [1]. It is generally obtained as a byproduct of copper and nickel mining [1, 4].

The manganese nodules found on the ocean floors are huge reserves of transition metals, containing tons of cobalt [1]. The top 3 cobalt reserve holding countries are the Democratic Republic of Congo (DRC), Australia, and Cuba while the top 3 producers include DRC, China, and Zambia [1].

History

Origin of its Name: The name is derived from ‘kobald’, German for “goblin” and from ‘cobalos’, a Greek word meaning “mine” [1, 2].

Who discovered it: The element was found by the Swedish chemist and mineralogist Georg Brandt [1].

When and How was it Discovered

The tomb of Tutankhamen, the ancient Egyptian Pharaoh who ruled during 1361-1352 BC, had a deep blue glass object that was made of cobalt [1]. In China, cobalt blue was used for making pottery glazes [1].

Aside from its ancient origins, its discovery in the recent times dates back to the 1730s when Georg Brandt was interested in a blue ore from some of the local mines [1]. Finally, he succeeded in proving that the blue ore contained a new metal [1]. He described its properties and published the results in 1739 [1, 3].

Cobalt Element

His discovery was controversial, as other chemists disputed his findings for many years [1]. However, his fellow Swedish chemist Torbern Bergman conducted further studies and confirmed Georg Brandt’s discovery in 1780 [1, 3].

Cobalt Identification

Atomic number 27 [1]
CAS number 7440-48-4 [1]
Position in the periodic table Group Period Block
  9 [1] 4 [1] d [1]

Properties and Characteristics of Cobalt

General Properties

Relative atomic mass 58.933 [1]
Atomic mass 58.933 amu [1]
Molar mass 58.9331950 ± 0.0000050 g/mol [6]
Molecular weight 58.933 g/mol [7]

Physical Properties

Color Silvery-blue, bluish-white [1, 4]
Melting point/freezing point 1495 °C, 2723 °F [1]
Boiling point 2927 °C, 5301 °F [1]
Density 8.86 g cm-3 [1]
State of matter at room temperature (solid/liquid/gas) Solid [1, 4]
Hardness
– Brinell 700 MPa [8]
– Mohs 5 [8]
– Vickers 1043 MPa [8]
Electrical Conductivity 1.7 X 107 S/m [8]
Ionic Charge 3+ [9]
Thermal (heat) conductivity 100 W/(m K) [8]
Specific heat 421 J kg-1 K-1 [1]
Bulk modulus Unknown [1]
Shear modulus Unknown [1]
Young’s modulus Unknown [1]
Vapor pressure
– Temperature (K) 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
– Pressure (Pa) 2.09 X 10-10 1.00 X 10-6 4.19 X 10-4 0.0379 1.15 16

Chemical Properties

Oxidation states 3, 2, 0, -1 [1]
Isotopes Isotope Mass Abundance (%) Half-life Mode of decay
  59Co 58.933 100

Cobalt Lewis Dot Structure

Atomic Data of Cobalt (Element 27)

Valence electrons 9 [10]
Quantum numbers
– n 3 [11]
– ℓ 2 [11]
– m -1 [11]
– ms -1/2 [11]
Electron configuration (noble gas configuration) [Ar] 3d74s2 [1]
Atomic structure
– Number of electrons 27 [4]
– Number of neutrons 32 [4]
– Number of protons 27 [4]
Radius of Atom
– Atomic radius 2.00 Å [1]
– Covalent radius 1.18 Å [1]
Electronegativity (Pauling-scale) 1.88 [1]
Electron affinity 63.873 kJ mol-1 [1]
Ionization energy (kJ mol-1) 1st 2nd 3rd 4th 5th 6th 7th 8th
  760.402 1648.356 3232.3 4949.7 7670.6 9842 12437 15225.4

Cobalt Electron Configuration (Bohr Model)

What is Cobalt Used for

  • Cobalt is alloyed for use in gas turbine generators and jet turbines because of its high-temperature strength and resistance to corrosion [1, 4].
  • Cobalt is occasionally used in electroplating owing to its hardness and attractive appearance [1].
  • It is commonly used as a cathode material in lithium ion batteries [4].
  • Cobalt salts are used to impart intense blue colors in glass, porcelain, pottery, enamels, and paint [1].
  • Radioactive 60Co is used for treating cancer, and in food irradiation for controlling pathogens and extending shelf life [1].
  • Stellite super-alloys, composed of chromium, cobalt, and tungsten, are used for making high temperature and high wear resistant cutting tools [2].

Cobalt Toxicity and Health Effects

Cobalt poisoning can take place when you accidentally ingest, breathe, or have it in contact with the skin in large amounts [12]. In large quantities, cobalt can be carcinogenic in humans and some animals [1].

It is found in trace amounts in humans and is an essential component of vitamin B12 [1]. Small doses of cobalt are also given to some animals to prevent mineral deficiencies in them [1].

Cobalt Mineral (Cobaltite)

Interesting Facts

  • Cobalt is graphically represented by a ‘kobold’ or goblin (considered troublesome by the medieval German miners) with some Chinese porcelain in the background, referring to its use as a pottery glaze in ancient China [1].
  • Cobalt can retain its magnetic properties up to a temperature (Curie Point) of 1,121 °C (2049.8 °F), the highest of all the ferromagnetic elements [3, 4].
  • In 2010, German scientists used a cobalt atom to capture the first pictures of spin changing [3].

Price of Cobalt

The cost of pure cobalt is about $0.21 per gram, and in bulk, it costs about $0.044 per gram [4].

References

  1. http://www.rsc.org/periodic-table/element/27/cobalt
  2. https://education.jlab.org/itselemental/ele027.html
  3. https://www.livescience.com/29275-cobalt.html
  4. https://www.chemicool.com/elements/cobalt.html
  5. https://education.jlab.org/itselemental/iso027.html
  6. https://www.webqc.org/molecular-weight-of-Co%28cobalt%29.html
  7. https://pubchem.ncbi.nlm.nih.gov/compound/cobalt#section=Top
  8. http://periodictable.com/Elements/027/data.html
  9. http://www.gpb.org/files/pdfs/gpbclassroom/chemistry/ionicChargesChart.pdf
  10. http://dwb4.unl.edu/Chem/CHEM869B/CHEM869BLinks/learn.chem.vt.edu/tutorials/bonding/valence.html
  11. http://chemistry-reference.com/q_elements.asp?Symbol=Co&language=en
  12. https://medlineplus.gov/ency/article/002495.htm

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