Ch.6 Ionic and Molecular Compounds

Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition

Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook

Timberlake 13th Edition

Ch.6 Ionic and Molecular Compounds

Problem 18b

Chapter 6, Problem 18b

Write the correct ionic formula for the compound formed between each of the following pairs of ions:
b. Ca²⁺ and S^2-

Verified step by step guidance

Identify the charges of the ions: Calcium (Ca) has a charge of +2 (Ca²⁺), and Sulfide (S) has a charge of -2 (S²⁻).

Determine the ratio of ions needed to balance the charges. Since the charges are equal in magnitude but opposite in sign (+2 and -2), one Ca²⁺ ion will combine with one S²⁻ ion to achieve charge neutrality.

Write the formula by placing the symbols of the cation (Ca) and anion (S) together, without including the charges, as they cancel each other out.

If necessary, use subscripts to indicate the number of each ion in the formula. In this case, no subscripts are needed because the ratio is 1:1.

The resulting ionic formula is the simplest whole-number ratio of the ions that balances the charges.

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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 positively charged ions (cations) and negatively charged ions (anions) bond together through electrostatic forces. The overall charge of the compound must be neutral, meaning the total positive charge must balance the total negative charge. Understanding this concept is crucial for determining the correct formula for any ionic compound.

Charge Balance

Charge balance is the principle that the total positive charge from cations must equal the total negative charge from anions in an ionic compound. For example, in the case of Ca²⁺ (which has a +2 charge) and S²⁻ (which has a -2 charge), one of each ion combines to achieve a neutral compound. This concept is essential for writing the correct ionic formula.

Chemical Formula Notation

Chemical formula notation is a way to represent the composition of a compound using symbols for the elements and numerical subscripts to indicate the number of each type of ion present. In the case of Ca²⁺ and S²⁻, the correct formula is CaS, indicating one calcium ion and one sulfide ion. Familiarity with this notation is important for accurately conveying the structure of ionic compounds.

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