Atomic number electron configuration oxidation states and uses of cobalt
Cobalt is a chemical element and ferromagnetic metal of Group 9 (VIIIb) of the periodic table, which can be used especially for heat-resistant and magnetic alloys. The symbol of Cobalt is Co. This metal was isolated (c.1735) by a Swedish chemist named Georg Brandt, though the cobalt compounds had been used for centuries to impart a blue colour to ceramics and glazes.
The oxidation number of cobalt in [Co(NH3)6]Cl2Br is given as +6, 0, +3, +2. Cobalt oxidation states are +2 and +3.
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About Cobalt
Cobalt metal has been detected in the Persian necklace beads and Egyptian statuettes of the 3rd millennium BCE, in glass, which is found in the Pompeii ruins, and in China as early as the Tang dynasty (618–907 CE) and after that, in the blue porcelain of the Ming dynasty (from 1368–1644). The term kobold was first applied (in the 16th century) to the ores thought to contain copper, but eventually, it is found to be poisonous arsenic-bearing cobalt ores. Finally, in 1742, Brandt determined that the blue colour of those ores was because of the presence of cobalt.
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Characteristics of Cobalt
Cobalt is a ferromagnetic metal having a specific gravity of 8.9. The Curie temperature is given as 1,115 °C, and the magnetic moment is given as 1.6–1.7 Bohr magnetons per atom. Cobalt contains a relative permeability two-thirds that of iron. Metallic cobalt is found as two crystallographic structures: fcc and hcp. The ideal transition temperature between the fcc and hcp structures is given as 450 °C, but in practice, the energy difference between them is so small that the random intergrowth of the two is very common.
Occurrence of Cobalt
The stable form of the cobalt metal can be produced in supernovae through the r-process. It comprises a percentage of 0.0029 of the crust of Earth. Free cobalt (which is the native metal) is not found on Earth due to the chlorine in the ocean and oxygen in the atmosphere. Both of these are abundant enough in the upper layers of the crust of Earth to prevent native metal cobalt from producing. Pure cobalt metal in the native metal produced on Earth is unknown, except as recently delivered in meteoric iron. Also, this element contains a medium abundance, whereas the natural compounds of cobalt are numerous, and the small amounts are found in most soils, rocks, animals, and plants.
Production of Cobalt
The primary ores of cobalt metal are erythrite, cobaltite, skutterudite, and glaucodot, but most cobalt can be obtained by reducing the cobalt by-products of copper and nickel mining and smelting.
Since cobalt is generally formed as a by-product, the supply of this metal depends, to a large extent, on the economic viability of the nickel and copper mining operations in the relevant market. Demand for this cobalt metal is projected to increase in 2017 by 6%.
Extraction of Cobalt
The U.S. Geological Survey estimates the world's cobalt reserves at 7,100,000 metric tons. And, Democratic Republic of the Congo (DRC) is currently producing 63% of the world's cobalt. By 2025, this market share can reach 73% if planned expansions by mining producers such as Glencore Plc take place as expected. However, by 2030, global demand could be 47 times more than that of 2017, as estimated by Bloomberg New Energy Finance.
Applications of Cobalt
There are many applications concerning cobalt metal. Let us discuss a few of them below:
Alloys
Superalloys of cobalt-based have historically consumed most of the cobalt formed. The stability of temperature of these alloys makes them suitable for turbine blades for aircraft jet engines and gas turbines, although the nickel-based single-crystal alloys will surpass them in performance. Also, the cobalt-based alloys are corrosion - and wear-resistant by making them, such as, useful for making orthopaedic implants that do not wear down over time.
Batteries
Lithium cobalt oxide (LiCoO2) can be used widely in lithium-ion battery cathodes. This material is mixed with cobalt oxide layers with lithium intercalated. During the discharge, the lithium releases lithium ions. Nickel metal hydride (NiMH) and Nickel-cadmium (NiCd) batteries also include cobalt to improve the nickel oxidation present in the battery. Transparency Market Research has estimated the global lithium-ion battery market at ﹩30 billion in 2015, and it is predicted to increase to over US﹩75 billion by 2024.
Health Impacts of Cobalt
Cobalt is considered an essential element for minute amounts of life. The LD50 value for the soluble cobalt salts has been estimated to be in a range of 150 - 500 mg/kg. In the US, the OSHA - Occupational Safety and Health Administration has designated a permissible exposure limit (PEL) of cobalt in the workplace as a TWA - Time-Weighted Average of 0.1 mg/m3. Also, the NIOSH - National Institute for Occupational Safety and Health has set a recommended exposure limit (REL) to 0.05 mg/m3, a time-weighted average. The Immediately Dangerous to Life and Health - IDLH value is given as 20 mg/m3.
FAQs on Cobalt Element Overview Structure Properties and Applications
1. What is cobalt in chemistry?
Cobalt is a chemical element with the symbol Co and atomic number 27, classified as a transition metal in Group 9 of the periodic table. It is a hard, lustrous, silver-gray metal known for its magnetic properties and high melting point.
- Electronic configuration: [Ar] 3d7 4s2
- Block: d-block element
- Common oxidation states: +2 and +3
- Occurs naturally in minerals such as cobaltite (CoAsS)
2. What is the electron configuration of cobalt?
The electron configuration of cobalt (Co, Z = 27) is [Ar] 3d7 4s2. This means cobalt has 27 electrons arranged as follows:
- Core configuration: [Ar] (18 electrons)
- Valence electrons: 3d7 4s2
3. What are the common oxidation states of cobalt?
The most common oxidation states of cobalt are +2 and +3. These oxidation states are typical for transition metals and arise from the loss of 4s and sometimes 3d electrons.
- Co2+: Very common in aqueous solutions and salts like CoCl2
- Co3+: Found in coordination compounds such as [Co(NH3)6]3+
4. What are the physical properties of cobalt?
Cobalt is a hard, ferromagnetic, silver-gray transition metal with a high melting point. Its key physical properties include:
- Atomic mass: 58.93 g mol-1
- Melting point: 1495 °C
- Boiling point: 2927 °C
- Density: 8.90 g cm-3
- Magnetic behavior: Ferromagnetic at room temperature
5. How does cobalt react with oxygen?
Cobalt reacts with oxygen on heating to form cobalt(II) oxide, CoO. The balanced chemical equation is:
2Co(s) + O2(g) → 2CoO(s)
- The reaction occurs more readily at elevated temperatures.
- In excess oxygen, mixed oxides such as Co3O4 can also form.
6. What are the uses of cobalt in chemistry and industry?
Cobalt is widely used in batteries, alloys, catalysts, and pigments due to its chemical stability and variable oxidation states. Major uses include:
- Lithium-ion batteries (e.g., lithium cobalt oxide, LiCoO2)
- Superalloys for jet engines and turbines
- Catalysts in petroleum refining and Fischer–Tropsch synthesis
- Cobalt blue pigments in ceramics and glass
7. What is cobalt(II) chloride and what is its formula?
Cobalt(II) chloride is an ionic compound with the formula CoCl2, containing cobalt in the +2 oxidation state. It is commonly encountered as:
- Anhydrous form: CoCl2 (blue solid)
- Hexahydrate: CoCl2·6H2O (pink solid)
8. Why is cobalt considered a transition metal?
Cobalt is considered a transition metal because it has a partially filled d-subshell in its atoms or common ions. Specifically:
- Atomic configuration: [Ar] 3d7 4s2
- Forms ions like Co2+ with incomplete 3d orbitals
- Exhibits variable oxidation states and forms colored compounds
9. What are some common cobalt compounds?
Common cobalt compounds include oxides, halides, and coordination complexes of cobalt(II) and cobalt(III). Examples are:
- CoO – cobalt(II) oxide
- Co3O4 – cobalt(II,III) oxide
- CoCl2 – cobalt(II) chloride
- [Co(NH3)6]3+ – a cobalt(III) coordination complex
10. Is cobalt magnetic and why?
Yes, cobalt is ferromagnetic at room temperature because it has unpaired electrons in its 3d orbitals. The presence of unpaired electrons allows magnetic moments to align in the same direction under an external magnetic field.
- Electron configuration: 3d7 contains unpaired electrons
- Displays ferromagnetism similar to iron and nickel
- Used in permanent magnets and magnetic alloys
