Question

Cobalt forms \(\mathrm{Co}^{2+}\) and \(\mathrm{Co}^{3+}\) ions. Write the formulas for the two cobalt oxides formed by these transition metal ions.

Short answer

The formulas for the two cobalt oxides are \( \mathrm{CoO} \) and \( \mathrm{Co_2O_3} \).

Step-by-step solution

Identify Cobalt Ion Charges

Cobalt can form two cations: \( \mathrm{Co}^{2+} \) and \( \mathrm{Co}^{3+} \). These charges will determine the two possible cobalt oxides.

Determine Oxide Ion Charge

The oxide ion has a charge of \( \mathrm{O}^{2-} \). This charge remains constant in all oxide compounds, meaning that each oxygen atom provides a \(-2\) charge.

Write Formula for CoO

Using the \( \mathrm{Co}^{2+} \) ion, balance the charges with the \( \mathrm{O}^{2-} \) ion. The simplest formula that balances these charges is \( \mathrm{CoO} \), where the charges are 2+ from cobalt and 2- from oxide, cancelling each other out.

Write Formula for Co2O3

Using the \( \mathrm{Co}^{3+} \) ion, combine it with the \( \mathrm{O}^{2-} \) ion. To balance the charges, two cobalt ions (total charge 6+) are needed for three oxide ions (total charge 6-). Therefore, the formula is \( \mathrm{Co_2O_3} \).

Key concepts

Transition Metal Ions

Transition metal ions are fascinating components in chemistry due to their ability to exhibit multiple oxidation states. This trait arises from the variable occupancy of their d-electron orbitals, allowing transition metals like cobalt to form different ions. Understanding these oxidation states is the key to predicting and writing chemical formulas for compounds involving transition metals like cobalt.

Cobalt, a transition metal, readily forms two different cations:

• Cobalt (II) ion, represented as \( \mathrm{Co}^{2+} \)
• Cobalt (III) ion, represented as \( \mathrm{Co}^{3+} \)

This flexibility in forming multiple charges is typical for transition metals and is essential for balancing charges in compound formation.

Knowing the specific oxidation states that cobalt can adopt is crucial in writing correct chemical formulas for its compounds. The oxidation state directly impacts the balance of charges in a compound, dictating how many of each ion is needed to achieve neutrality.

Charge Balance in Compounds

Charge balance is a fundamental principle in chemistry that ensures compounds are stable. In any compound, the sum of positive charges must equal the sum of negative charges. This principle guides us when combining different ions to form neutral compounds.

To determine the chemical formula of a compound, such as cobalt oxides, we start by balancing the positive charges from the cobalt ions with the negative charges from the oxide ions. Here's how this is accomplished:

For \( \mathrm{CoO} \):

• The cobalt (II) ion, \( \mathrm{Co}^{2+} \), has a charge of +2.
• The oxide ion, \( \mathrm{O}^{2-} \), has a charge of -2.
• Combining one \( \mathrm{Co}^{2+} \) ion with one \( \mathrm{O}^{2-} \) ion gives a neutral compound, because the charges cancel each other out.

In \( \mathrm{Co_2O_3} \):

• Each cobalt (III) ion, \( \mathrm{Co}^{3+} \), carries a charge of +3.
• To neutralize the total positive charge of +6 (from two \( \mathrm{Co}^{3+} \) ions), three oxide ions \( \mathrm{O}^{2-} \) are required, each contributing a -2 charge.
• This results in a balanced compound formula of \( \mathrm{Co_2O_3} \).

Chemical Formulas

Chemical formulas are concise representations of the composition of molecules and compounds. They tell us not only which elements are present but also the ratio in which they combine. To write chemical formulas, especially for compounds including metals like cobalt, it's important to understand both the symbol of the elements and their respective charges.

In the case of cobalt oxides, the formulas are determined by:

• Understanding the charges of the ions involved (\( \mathrm{Co}^{2+} \) and \( \mathrm{Co}^{3+} \).
• Knowing the constant charge of the oxide ion, which is always \( \mathrm{O}^{2-} \).
• Applying the principle of charge neutrality to balance the formula.
• Formulating the compound's simplest whole-number ratio, resulting in compounds like \( \mathrm{CoO} \) and \( \mathrm{Co_2O_3} \).

These formulas not only reflect finding the simplest ratios that balance electrical charges but also ensure that the compounds are correctly represented as neutral. They are essential for understanding and communicating the nature of chemical interactions at the molecular level.