Question

What are the charges of the ions in an ionic compound containing cobalt(III) and fluoride ions? Write the formula for the compound.

Short answer

The charges are \( \text{Co}^{3+} \) and \( \text{F}^{-} \). The compound's formula is \( \text{CoF}_3 \).

Step-by-step solution

Identify the Charge of the Cobalt Ion

The compound contains cobalt(III) ions. The Roman numeral III represents the charge of the cobalt ion, meaning cobalt has a charge of +3 when it forms an ion. Therefore, the cobalt ion is written as \( \text{Co}^{3+} \).

Determine the Charge of the Fluoride Ion

Fluoride ions are derived from fluorine, which is in Group 17 (halogens) and typically forms ions with a charge of -1. Therefore, each fluoride ion carries a charge of \( \text{F}^{-} \).

Balancing the Charges

In an ionic compound, the total positive charge must balance the total negative charge. We have \( \text{Co}^{3+} \) as the positive ion and \( \text{F}^{-} \) as the negative ion. A charge of +3 from one cobalt ion can be balanced by using three fluoride ions, each having a charge of -1.

Write the Compound Formula

Since it takes one cobalt ion to balance three fluoride ions to achieve charge neutrality, the formula for the ionic compound is \( \text{CoF}_3 \).

Key concepts

Cobalt(III) Ion

Cobalt(III) ion is a specific type of ion formed by the element cobalt. When we mention cobalt(III), the Roman numeral "III" is crucial. It represents the oxidation state or charge of the cobalt ion, which is +3. In chemical notation, it is written as \( \text{Co}^{3+} \). This means that a cobalt atom has lost three electrons to become positively charged.

Cobalt can have various oxidation states, but in this case, the "III" indicates that it is in its +3 state, making it more reactive and eager to combine with a negatively charged ion like fluoride. Understanding this charge helps us predict how cobalt will behave in compounds.

Fluoride Ion

A fluoride ion is derived from a fluorine atom. Fluorine is part of the halogens, which are placed in Group 17 of the periodic table. These elements are known for forming ions with a negative charge. When fluorine gains an electron, it forms a fluoride ion with a charge of \( \text{F}^{-} \).

The negative charge occurs because the fluorine atom has one more electron than protons, leading to an extra negative charge. The fluoride ion's charge is always -1, making it straightforward to predict its behavior in forming ionic compounds.

• Fluoride is crucial in many applications, from dental care to water treatment, illustrating the importance of halogen ions.

Chemical Formula

The chemical formula for an ionic compound shows the types and numbers of ions present in the compound. It provides insight into how ions are arranged to maintain balance.

In the case of cobalt(III) and fluoride ions, the chemical formula is \( \text{CoF}_3 \). This formula arises because we need three fluoride ions, each with a charge of -1, to balance one cobalt ion with a +3 charge.

To write chemical formulas correctly, it is vital to know the charges of the involved ions. This ensures the total positive and negative charges in the compound balance. Creating balanced formulas is fundamental to writing chemical equations and predicting how substances will interact.

Charge Neutrality

Charge neutrality is a cornerstone concept in chemistry, especially in forming ionic compounds. It means the total positive charge and total negative charge in a compound must equal each other, resulting in no overall charge.

For the cobalt(III) and fluoride ion compound, achieving charge neutrality involves balancing their charges:

• Cobalt(III) ion contributes a +3 charge.
• Each fluoride ion contributes a -1 charge.

By using three fluoride ions to balance one cobalt(III) ion, we achieve charge neutrality, encapsulated in the chemical formula \( \text{CoF}_3 \).

This balance ensures the stability of the ionic compound and is a key factor in predicting the structure and properties of chemical compounds.