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Ch.2 - Atoms, Molecules, and Ions
Chapter 2, Problem 62d

Predict the chemical formulas of the compounds formed by the following pairs of ions: (d) Cd2+ and CO32-

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1
Identify the charges of the ions involved. In this case, Cd2+ has a charge of +2 and CO3^2- (carbonate ion) has a charge of -2.
Determine the simplest ratio of ions that will result in a neutral compound. Since the charges are +2 and -2, they can combine in a 1:1 ratio to balance each other out.
Write the chemical formula by placing the cation (Cd2+) first and the anion (CO3^2-) second. As they combine in a 1:1 ratio, the formula will include one of each ion.
Check the formula to ensure the total charge is zero. The +2 charge from Cd2+ and the -2 charge from CO3^2- cancel each other out, confirming the compound is neutral.
The predicted chemical formula for the compound formed by Cd2+ and CO32- is CdCO3.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Compounds

Ionic compounds are formed when cations (positively charged ions) and anions (negatively charged ions) bond together through electrostatic forces. The overall charge of the compound must be neutral, meaning the total positive charge from the cations must balance the total negative charge from the anions.
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Charge Balance

In order to predict the formula of an ionic compound, it is essential to ensure that the charges of the ions balance each other. For example, if a cation has a charge of +2 and an anion has a charge of -2, one of each ion will combine to form a neutral compound. This principle is crucial for determining the correct ratio of ions in the formula.
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Common Ions and Their Charges

Understanding the common ions and their respective charges is vital for predicting chemical formulas. In this case, cadmium (Cd) typically forms a +2 charge, while carbonate (CO3) has a -2 charge. Recognizing these charges allows for the correct assembly of the ions into a stable compound.
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