Charge Of Cobalt And The Reactions It Undergoes

Cobalt is a multivalent transition metal. As a transition metal, cobalt has multiple valency and can exhibit more than one charge. This is a common characteristic across transition metals, except for zinc, silver, and cadmium.

As a metal, cobalt will lose electrons to form a cation. The number of electrons it loses determines the charge. When metals lose electrons, there is a higher number of protons than electrons which accounts for the positive charge.

In this article, I’ll be discussing the ionic charge and nuclear charge of cobalt, among other peculiar characteristics.

Properties of cobalt

  • Cobalt is a transition metal located in group 9 (VIIIB) and period 4 of the periodic table
  • It is also located in the d-block
  • Cobalt has an atomic number of 27 and a mass number of 58.933 g/mol
  • Cobalt has an electronic configuration of [Ar]3d74s2 with 2, 8, 15 & 2 electrons in its shells
  • It is one of the three metals that are ferromagnetic at room temperature
  • Cobalt exists in the Earth’s crust in combination with other compounds. When it exists in its free form, it is found in alloys of natural meteoric iron. This pure cobalt can only be gotten through reductive smelting
  • It is naturally hard with a silver luster but is used to give jewelry, glass, and paint a blue tint
  • Cobalt is also present in the sun and stellar atmospheres, natural waters, soils, plants, animals, vitamin B12, and minerals such as cobaltite, smaltite, heterogenite, and erythrite
  • This metal can form compounds with a wide range of oxidation states. The most common states are +2 and +3, but it could be anywhere between -3 to +5
  • In addition, cobalt is a solid near room temperature with a density of 8.90 g/cm3. But, at its melting point, its density drops to 8.86 g/cm3
  • It has a boiling point of 5,301°F (2,927°C) and a melting point of 2,723°F (1,767°C)

What is the charge of cobalt?

Cobalt can have a +2 or a +3 charge, depending on its oxidation state in the compound and how many electrons it lost to form bonds with other elements.

Co2+ is known as the cobaltous cation while Co3+ is the cobaltic cation. For instance, when these actions form cobalt chloride with chlorine, Co2+ forms cobaltous chloride or cobalt (II) chloride, and Co3+  forms cobaltic chloride or cobalt (III) chloride.

What is the nuclear charge of cobalt?

Nuclear charge is the total positive charge on the nucleus of an atom. It is the same as the atomic number and the total number of protons in that atom. Therefore, the nuclear charge of cobalt is 27.

What are the reactions cobalt undergoes?

With water

Water, at room temperature, has little to no effect on cobalt metal. But, water as steam will react with red hot cobalt metal to produce cobalt(II) oxide, CoO.

2Co (s) + O2 (g) ———> 2CoO (s)

With air

Cobalt will not react with oxygen until heat is applied. Upon heating air, Co3O4, an oxide of cobalt, forms. As more heat is applied, cobalt(II) oxide, CoO, is formed.

3Co (s) + 4O2 (g) ———> 2Co3O4 (s)

2Co (s) + O2 (g) ———> 2CoO (s)

With acids

Cobalt reacts with most acids and emits hydrogen gas. Considering its reaction with sulphuric acid, it forms a pink solution that contains Co2+ and releases hydrogen gas.

However, the cobalt ion is not by itself in the solution. It is present as a complex [Co(OH2)6]2+, hexaaquacobalt(II) complex ion.

Co (s) + H2SO4 (aq)  ———> Co2+(aq) + SO42−(aq) + H2 (g)

With halogens

Cobalt forms colored cobalt dihalides with the halogens.

  • Co + Cl2 (g) ———> CoCl2 (s) (red)
  • Co + Br2 (l) ———> CoBr2 (s) (green)
  • Co + I (s) ———> CoI2 (s) (blue-black)

With hydroxide

When cobalt reacts with hydroxide ions, it precipitates Co2+ ion out of pink complex solution ([Co(H2O)6]2+).

[Co(H2O)6]2+(aq) + 2OH(aq)  ———>  [Co(OH)2(H2O)4] (s) + 2H2O (l)

It oxidizes into dark brown cobalt(III) hydroxide in excess hydroxide,

[Co(OH)2(H2O)4] (s) + O2 (g) + H2O (l) ———> Co(OH)3 (s) [dark brown]

With sulfide ion

When sulfide ions in weakly acidic H2S or slightly alkaline Na2S react with the cobalt metal, it precipitates Co2+. However, the cobalt ion is still in a compound with sulfur.

Co2+(aq) + S2−(aq) ———> CoS (s)

Upon reaction with nitric acid, the compound dissociates in a stable cobalt(II) ion, sulfur, nitrogen oxide, and water.

CoS (s) + 2NO3(aq) + 8H+(aq) ———> 3Co2+(aq) + 3S (s) + 2NO (g) + 4H2O (l)

With ammonia

Cobalt metal reacts with ammonia and precipitates blue or pink cobalt(II) ions. The precipitate is a complex that will dissolve in excess ammonia and the presence of oxygen to further produce cobalt(III) ions.

[Co(H2O)6]2+(aq) + 2NH3 (aq)  ———> [Co(OH)2(H2O)4] (s) + 2NH4+(aq)

[Co(OH)2(H2O)4](s) + 6NH3 (aq) ———> [Co(NH3)6]2+(aq) + 4H2O (l) + 2OH(aq)

[Co(NH3)6]2+(aq) ———> [Co(NH3)6]3+(aq) + e

Formation of complexes

Cobalt can form complexes with thiocyanate, SCN. In acidic and neutral environments, cobalt forms blue or red complexes with thiocyanate.

Co(H2O)6]2+(aq) + SCN(aq) ———>  [Co(H2O)5(SCN)]+(aq) + H2O (l)

[Co(H2O)6]2+(aq) + 4SCN(aq) ———>  [Co(SCN)4]2−(aq) + 5H2O (l)


What is the charge of Co in CoCl2?

The charge of Co in CoCl2, cobalt(II) chloride, is +2. This can be determined by substituting the oxidation state of Cl, -1, into the chemical formula.

Co + 2(-1) = 0

Co = +2

What is the charge of Co in CoSO4?

The sulfate in CoSO4, cobalt sulfate, has a charge of -2. Substituting this into the chemical formula,

Co + (-2) = 0

Co = +2

Therefore, the charge of cobalt in CoSO4 is +2.

What is the charge of Co in Co(NO3)2?

The charge of the nitrate ion is -1. Substitute it into the chemical formula and equate it to the overall charge of the chemical compound.

Co + 2(-1) = 0

Co = +2


Cobalt is more multivalent than monovalent. The most common oxidation states are +2 and +3. These oxidation states largely influence the charge of this transition metal. As mentioned earlier, a common characteristic of transition metals is the multiple oxidation states and charges.

Another characteristic is its ability to form colored complexes, a common property of transition metals. Additionally, besides the +2 and +3 charges, cobalt can also have a +4 charge in an octahedral environment.

Learn further with this guide on how to find the charge of transition metals.

Thanks for reading.