Problem 36 - Chemistry Matter and Change

Question

Apply lon \(X\) has a charge of \(2+,\) and ion \(Y\) has a charge of \(1-.\) Write the formula unit of the compound formed from the ions.

Step-by-Step Solution

Answer

The formula unit of the compound is \(XY_2\).

Step 1: Identify the Charges of the Ions

The ion \(X\) has a charge of \(2+\), and the ion \(Y\) has a charge of \(1-\). These are the charges each ion will contribute in the chemical compound.

Step 2: Determine the Ratio of Ions Required

To form a neutral compound, the total positive charge must equal the total negative charge. Since ion \(X\) has a \(2+\) charge, and ion \(Y\) has a \(1-\) charge, you will need two \(Y\) ions to balance the charge of one \(X\) ion. This gives a neutral compound because \(2+\) from \(X\) cancels with two \((1-)\) charges from two \(Y\) ions.

Step 3: Write the Formula Unit

Use the ratio determined in the previous step to write the formula unit. The formula unit for the compound will be \(XY_2\), indicating one \(X\) ion and two \(Y\) ions. It shows that the charges balance out: \(2+\) from \(X\) and \((-1)\times2=-2\) from \(Y_2\).

Key Concepts

Ionic Compounds

Ionic compounds form when positively charged ions, known as cations, and negatively charged ions, known as anions, come together. The attractive force between these oppositely charged ions results in a stable ionic compound. Ionic compounds are often found in a crystalline solid state and have distinct properties, such as high melting and boiling points. They conduct electricity when dissolved in water or melted. This is because the ions become free to move, allowing for the flow of electric current.In the exercise provided, ion \(X\) has a \(2+\) charge indicating it loses 2 electrons to become stable, while ion \(Y\) has a \(1-\) charge indicating it gains one electron. These ions interacting due to their opposite charges form the basis of the compound's structure.

Charge Balance

The concept of charge balance is essential in forming ionic compounds. It ensures that the total positive and negative charges in a compound are equal, resulting in a stable and neutral chemical structure. This means the sum of the charges from the ions must equal zero.In problems like the one given, understanding charge balance helps us determine the ratio of ions needed. For instance, the 2+ charge from ion \(X\) needs two ions of \(Y\) with a 1- charge each to achieve neutrality:

• 1 \(X^{2+}\) contributes a +2 charge.
• 2 \(Y^{-}\) ions each contribute a -1 charge, for a total of -2.
• Together, they sum up to zero, balancing the charges and achieving a neutral compound.

Neutral Compound

A neutral compound is one where the total positive and negative charges balance each other out to result in a charge of zero. This is crucial for the stability of the compound, as any imbalance could lead to additional reactions as the compound seeks stability.The formula unit of an ionic compound represents the smallest whole-number ration of ions that exhibits this charge balance. In the exercise, the neutral compound is represented by the formula \(XY_2\). This indicates that the single, positively charged ion \(X^{2+}\) is balanced by two negatively charged \(Y^{-}\) ions, providing a stable, neutral entity with net charge of zero.