How to Find the Valency of Cobalt?

Cobalt (Co) is a transition metal, and unlike elements in groups 1, 2, and 13-18, it can exhibit multiple valencies. Its common valencies are +2 and +3. Therefore, there isn't one single valency for cobalt. To determine cobalt's valency in a specific compound, you need to consider the other elements present and their known charges.

Determining Cobalt's Valency in a Compound

Here's how to determine the valency of cobalt in a given compound:

1. Identify the other elements present: Note all the elements that cobalt is bonded to in the compound.

2. Determine the charges of the other elements: Look up the common oxidation states (charges) of the other elements. For example, oxygen usually has a -2 charge.

3. Determine the overall charge of the compound: If the compound is neutral (which is most common), the sum of all the charges must equal zero. If the compound is an ion, the sum of the charges must equal the charge of the ion.

4. Set up an equation to solve for cobalt's valency: Let 'x' represent the valency of cobalt. Use the charges of the other elements and the overall charge of the compound to set up an algebraic equation.

5. Solve for x: Solve the equation to find the value of x, which represents the valency of cobalt in that specific compound.

Examples

• Cobalt(II) Oxide (CoO):

  • Oxygen has a valency of -2.
  • The compound is neutral (overall charge is 0).
  • Equation: x + (-2) = 0
  • Solving for x: x = +2
  • Therefore, the valency of cobalt in CoO is +2.

• Cobalt(III) Oxide (Co₂O₃):

  • Oxygen has a valency of -2.
  • The compound is neutral (overall charge is 0).
  • Equation: 2x + 3(-2) = 0
  • Solving for x: 2x - 6 = 0 => 2x = 6 => x = +3
  • Therefore, the valency of cobalt in Co₂O₃ is +3.

• Cobalt(II) Chloride (CoCl₂):

  • Chlorine has a valency of -1.
  • The compound is neutral (overall charge is 0).
  • Equation: x + 2(-1) = 0
  • Solving for x: x - 2 = 0 => x = +2
  • Therefore, the valency of cobalt in CoCl₂ is +2.

Conclusion

Since Cobalt is a transition metal, it can have multiple valencies, most commonly +2 and +3. To determine the valency of cobalt in a specific compound, you need to consider the charges of the other elements in the compound and the overall charge of the compound.