Cobalt (Co)

Cobalt is a chemical element with an atomic number of 127 in the periodic table of elements. It occurs abundantly in Earth’s crust, but mostly in a compound form. This strong ferromagnetic element is a member of the transition metals family in the periodic table. Having two valence electrons, cobalt is a relatively active but highly magnetic element, forming many compounds with other chemical elements.

Chemical and Physical Properties of Cobalt

Property	Value
Symbol	Co
Name	Cobalt
Atomic number	27
Atomic weight	58.9332 g.mol-1
Group	8 (Transition metal)
Period	4
Color	A lustrous silvery-white metal with a bluish hue
Physical state	Solid at room temperature
Electronegativity	1.8
Density	8.9 g.cm-3 at 20°C
Melting point	1495 °C
Boiling point	2927 °C
Ionic radius	0.078 nm (+2) ; 0.063 nm (+3)
Isotopes	8 (1 stable isotope)
Most characteristic isotope	cobalt-60
Electronic shell	[Ar] 3d7 4s2
The energy of the first ionization	757 kJ.mol-1
The energy of the second ionization	1666.3 kJ.mol-1
Discoverer	Georg Brandt
Year	1737

With the periodic table symbol (Co), atomic number 27, atomic mass of 58.9332 g.mol-1, and electron configuration  [Ar] 3d7 4s2, cobalt reaches its boiling point at 2927 °C, while the melting point is achieved at 1495 °C. This brittle and strong ferromagnet retains its magnetism even at high temperatures, i.e. it has the highest Curie point of all metals in the periodic table of elements.

Due to this, cobalt is one of the three naturally occurring magnetic metals (along with nickel and iron). This lustrous silvery-white metal is highly reactive with acids but non-reactive with H2O molecules. 

Having an electronegativity of 1.8 according to Pauling, +4 oxidation state, and atomic radius according to van der Waals of 0.125 nm, the electron configuration of this transition metal remains stable in contact with air. Cobalt is resistant to burning as a metal, though the same is not true for its powdery form. 

How Was Cobalt Discovered?

The first known evidence of cobalt was found in the cultural remains of ancient Babylon and Egypt. These people have used cobalt as a source of blue dye for the decoration of pottery and glass. The Tang (600-900 AD) and Ming dynasties (1350-1650 AD) of ancient China are famous for their blue decorated porcelain. These civilizations used to obtain the rich blue pigment mainly from the cobalt salts. 

In 1739, Swedish chemist Georg Brandt (1694 – 1768) attempted an experiment with copper-resembling ore, i.e. kobold. He conducted this research in an effort to oppose the belief of the alchemists and prove that bismuth and arsenic do not produce the blue pigment. Brandt managed to isolate the pure elemental form of cobalt, i.e. the cobalt metal via the fire assay procedure.

How Did Cobalt Get Its Name?

Brandt managed to isolate the pure elemental form of cobalt from the ore labeled by the German miners as ‘kobold’ – a medieval German word meaning ‘goblin’. The reason behind this uncommon name choice was the strong conviction and belief of the miners that goblins living in the Schneeberg Mountains had put a spell on this ore. This comes from the fact that the ore they were mining resembled natural copper deposits, but they still couldn’t exploit and separate any copper from it. 

When Brandt discovered the new element, he remembered the story and found it most suitable to name the element cobalt. He wrote about his newly discovered element under this name in his scientific research, published under the original title “Dissertatio de Semi-Metallis”. 

Where Can You Find Cobalt?

In its elemental form, cobalt occurs in the core of Earth and the Sun, but in extremely small quantities. Cobalt is more frequently found as a part of compounds in nature. It can also be found as a trace element in humans, animals, seawater, and plants.

Most commonly, this substance is nowadays obtained as a by-product in the mining of nickel and copper, i.e. from the nickel-copper sulfide deposits and the nickel-bearing laterites. The largest cobalt deposits in the United States are in Alaska, California, Idaho, Montana, North Carolina, Maine, Michigan, Minnesota, Missouri, New Mexico, Oregon, Pennsylvania, Puerto Rico, and Tennessee. 

The Democratic Republic of the Congo, Zambia, Finland, Azerbaijan, Kazakhstan, China, and Russia, count among the world’s largest cobalt producing countries. They also represent locations that have the highest quantities of cobalt ores, such as cobaltite, skutterudite, erythrite, and glaucodot. 

Cobalt in Everyday Life

Due to its strong magnetic, thermal, and anti-corrosive properties, the use of cobalt has various applications in everyday life. This transition metal can be found in many industries, production processes, and products we frequently use:

• Medical treatment of anemia;
• Making of dental plates;
• Manufacturing of non-corrosive metal implants and prosthetics;
• Manufacturing of Vitamin B12;
• Magnetic recording media;
• Electroplating, due to its non-corrosive properties;
• Making of high-speed and high-temperature cutting tools;
• Cobalt blue pigment is used for decoration of pottery, glass, in painting colors;
• Production of metal-plated items, such as buttons, zippers, tools, utensils;
• Manufacturing of hair dyes, drying agents for inks and varnishes;
• Making of turbine blades for gas turbines and aircraft jet engines;
• Manufacturing of rechargeable batteries for smartphones and laptops;
• The radioisotope cobalt-60 is used in medicine for food sterilization and inspection of the inner bodily organs and tissues.

Cobalt and Vitamin B12

Vitamin B12, or cyanocobalamin (C63H88CoN14O14P), is one of the most essential vitamins for the proper functioning of the central nervous system, and the healthy blood cell formation mechanism of the body. It’s a crystallizable cobalt complex consisting of cobalt-containing biomolecules as vital components.

Vitamin B12 deficiency can result in:

• Alzheimer’s disease;
• Memory loss; 
• Heart failure;
• Depression;
• Poor muscle function;
• Ataxia;
• Irritability;
• Eating disorders;
• Tiredness;
• Blood clots. 

Meat and dairy products are an excellent food source of Vitamin B12. Due to this, people who implement a vegan diet are at the highest risk of having low levels of vitamin B12 in the body, which is of vital importance for the relay of sensory information from the neuron cells to the corresponding brain processing and controlling areas. 

How Dangerous Is Cobalt?

When German miners worked on locations rich in cobalt ore near Saxony, they frequently complained of adverse health effects with tragic consequences, possibly caused by the fumes raised from the ore excavation. Since very few chemical elements were known at that time, they assigned the health hazards to kobolds. 

After George Brandt managed to isolate cobalt as a new chemical element and determine its properties, the eye of science had turned more onto the health benefits and hazards of this transition metal. Today, cobalt is classified as a potentially carcinogenic substance according to the International Agency for Research on Cancer (IARC). 

Environmental Effects of Cobalt

Cobalt mining is one of the greatest pollutants of the environment. Being one of the main components in the manufacturing process of rechargeable lithium-ion batteries for smartphones and laptops, or even electric car batteries (for electric vehicles such as Tesla), this magnetic metal is nowadays the most demanded substance that creates global cobalt supply chains. The enormous expansion of the cobalt market has triggered extensive mining which is a process that produces toxic dust and fumes in the mines’ surroundings. 

Being a producer of over 63% of the global cobalt supplies, the Democratic Republic of the Congo (DRC), especially the bigger cities like Lubumbashi and Likasi, struggle with enormous pollution of the living environment, as well as contamination of the surrounding land and waters by mining wastes. These abusive practices of the large electronic companies are considered as discrimination against the human rights of the Congolese people. 

Not only does this toxic cobalt dust and waste contaminate the environment, but it also leads to adverse effects upon human health. Namely, the prolonged exposure to the polluted air and the dust and fumes that come out during cobalt production results in lung diseases (pneumonia, asthma, lung edema), or even toxic allergy to cobalt. 

Isotopes of Cobalt

With a half-life of 5.27 years, cobalt-60 is the longest living radioactive isotope of cobalt. It’s obtained by irradiation of the cobalt-59 stable isotope in a nuclear reactor. 

Nuclide [n 1]	Z	N	Isotopic mass (Da) [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6]	Spin and parity [n 7][n 4]	Natural abundance (mole fraction)
	Excitation energy[n 4]							Normal proportion	Range of variation
47Co	27	20	47.01149(54)#				7/2−#
48Co	27	21	48.00176(43)#		p	47Fe	6+#
49Co	27	22	48.98972(28)#	<35 ns	p (>99.9%)	48Fe	7/2−#
					β+ (<.1%)	49Fe
50Co	27	23	49.98154(18)#	44(4) ms	β+, p (54%)	49Mn	(6+)
					β+ (46%)	50Fe
51Co	27	24	50.97072(16)#	60# ms [>200 ns]	β+	51Fe	7/2−#
52Co	27	25	51.96359(7)#	115(23) ms	β+	52Fe	(6+)
52mCo	380(100)# keV			104(11)# ms	β+	52Fe	2+#
					IT	52Co
53Co	27	26	52.954219(19)	242(8) ms	β+	53Fe	7/2−#
53mCo	3197(29) keV			247(12) ms	β+ (98.5%)	53Fe	(19/2−)
					p (1.5%)	52Fe
54Co	27	27	53.9484596(8)	193.28(7) ms	β+	54Fe	0+
54mCo	197.4(5) keV			1.48(2) min	β+	54Fe	(7)+
55Co	27	28	54.9419990(8)	17.53(3) h	β+	55Fe	7/2−
56Co	27	29	55.9398393(23)	77.233(27) d	β+	56Fe	4+
57Co	27	30	56.9362914(8)	271.74(6) d	EC	57Fe	7/2−
58Co	27	31	57.9357528(13)	70.86(6) d	β+	58Fe	2+
58m1Co	24.95(6) keV			9.04(11) h	IT	58Co	5+
58m2Co	53.15(7) keV			10.4(3) μs			4+
59Co	27	32	58.9331950(7)	Stable			7/2−	1.0000
60Co	27	33	59.9338171(7)	5.2713(8) y	β−, γ	60Ni	5+
60mCo	58.59(1) keV			10.467(6) min	IT (99.76%)	60Co	2+
					β− (.24%)	60Ni
61Co	27	34	60.9324758(10)	1.650(5) h	β−	61Ni	7/2−
62Co	27	35	61.934051(21)	1.50(4) min	β−	62Ni	2+
62mCo	22(5) keV			13.91(5) min	β− (99%)	62Ni	5+
					IT (1%)	62Co
63Co	27	36	62.933612(21)	26.9(4) s	β−	63Ni	7/2−
64Co	27	37	63.935810(21)	0.30(3) s	β−	64Ni	1+
65Co	27	38	64.936478(14)	1.20(6) s	β−	65Ni	(7/2)−
66Co	27	39	65.93976(27)	0.18(1) s	β−	66Ni	(3+)
66m1Co	175(3) keV			1.21(1) μs			(5+)
66m2Co	642(5) keV			>100 μs			(8-)
67Co	27	40	66.94089(34)	0.425(20) s	β−	67Ni	(7/2−)#
68Co	27	41	67.94487(34)	0.199(21) s	β−	68Ni	(7-)
68mCo	150(150)# keV			1.6(3) s			(3+)
69Co	27	42	68.94632(36)	227(13) ms	β− (>99.9%)	69Ni	7/2−#
					β−, n (<.1%)	68Ni
70Co	27	43	69.9510(9)	119(6) ms	β− (>99.9%)	70Ni	(6-)
					β−, n (<.1%)	69Ni
70mCo	200(200)# keV			500(180) ms			(3+)
71Co	27	44	70.9529(9)	97(2) ms	β− (>99.9%)	71Ni	7/2−#
					β−, n (<.1%)	70Ni
72Co	27	45	71.95781(64)#	62(3) ms	β− (>99.9%)	72Ni	(6-,7-)
					β−, n (<.1%)	71Ni
73Co	27	46	72.96024(75)#	41(4) ms			7/2−#
74Co	27	47	73.96538(86)#	50# ms [>300 ns]			0+
75Co	27	48	74.96833(86)#	40# ms [>300 ns]			7/2−#

Cobalt Compounds and Alloys

Being highly reactive, cobalt forms numerous compounds and alloys. This chemical element mostly occurs in a form of minerals, such as:

• Cobaltite (a cobalt sulfo-arsenide mineral);
• Linnaeite (a sulfide mineral);
• Skutterudite (a range of cobalt and nickel minerals); 
• Smaltite (a cobalt-nickel arsenide).

What Are Superalloys?

The complex alloys based on Group VIIIB elements (Ni, Fe, Co, and Cr) that are resistant to high thermal exposure and pressure are known as superalloys. 

Extensive List of Cobalt Compounds

• CeCoIn5
• Cerulean
• Cobalt blue
• Cobalt boride
• Cobalt disilicide
• Cobalt germanide
• Cobalt green
• Cobalt monosilicide
• Cobalt oxide nanoparticle
• Cobalt(II,III) oxide
• Cobalt(II) hydride
• Dicobalt edetate
• Dicobalt silicide
• Fluomine
• Hexol
• Lanthanum strontium cobalt ferrite
• Lithium cobalt oxide
• Lithium nickel cobalt aluminium oxides
• Lithium nickel manganese cobalt oxides
• Percobaltate
• Potassium cobaltinitrite
• Salcomine
• Sodium cobalt oxide
• Sodium cobaltinitrite
• Cobalt sulfide
• Cobalt(II) acetate
• Cobalt(II) bromide
• Cobalt(II) carbonate
• Cobalt(II) chlorate
• Cobalt(II) chloride
• Cobalt(II) cyanide
• Cobalt(II) fluoride
• Cobalt(II) formate
• Cobalt(II) hydroxide
• Cobalt(II) iodide
• Cobalt(II) naphthenate
• Cobalt(II) nitrate
• Cobalt(II) oxalate
• Cobalt(II) oxide
• Cobalt(II) phosphate
• Cobalt(II) phosphide
• Cobalt(II) selenide
• Cobalt(II) sulfate
• Cobalt(II) thiocyanate
• Bromopentaamminecobalt(III) bromide
• Chloro(pyridine)cobaloxime
• Chloropentamminecobalt chloride
• Cobalt(III) chloride
• Cobalt(III) fluoride
• Cobalt(III) hydroxide
• Cobalt(III) nitrate
• Cobalt(III) oxide
• Cis-Dichlorobis(ethylenediamine)cobalt(III) chloride
• Trans-Dichlorobis(ethylenediamine)cobalt(III) chloride
• Hexamminecobalt(III) chloride
• Lanthanum cobaltite
• Nitropentaamminecobalt(III) chloride
• Tris(ethylenediamine)cobalt(III) chloride

Cobalt Alloys

• Alacrite (also: L-605, Cobalt L-605, Haynes 25, and occasionally F90);
• Alnico – An aluminum, nickel, and cobalt alloy applied in the production of the most powerful magnets;
• Cobalt-chrome (also: Cobalt-chromium [CoCr]);
• Havar (UNS R30005) – A non-magnetic alloy of cobalt;
• Megallium – An alloy made up of 60% cobalt, 20% chromium, 5% molybdenum, and traces of other substances;
• Permendur – A cobalt-iron soft ferromagnetic alloy;
• Samarium–cobalt (SmCo) – A type of a rare-earth magnet;
• Stellite – A cobalt-chrome alloy, also comprising molecules of carbon, tungsten, and molybdenum;
• Vitallium – A 65% cobalt, 30% chromium, and 5% molybdenum alloy. 

5 Interesting Facts and Explanations

1. Cobalt is the 32nd most abundant element that can be found in Earth’s crust.
2. Curie temperature (TC), or Curie point, refers to the temperature degree above which the permanent magnetic properties of an element are lost. 
3. Ferromagnetism is a property displayed by cobalt, iron, nickel, along with the rare-earth elements gadolinium and dysprosium. This magnetic phenomenon occurs at the atomic level of the chemical elements and materials that form permanent magnets or are easily attracted by a magnetic field. 
4. Ferromagnetic elements possess the strongest magnetic properties. 
5. Georg Brandt was the first chemist that dispelled the ancient alchemist belief that silver can be transmuted into gold.