Writing and Naming Ionic Compounds Assessment

1. What is the chemical formula of potassium sulfide?

KS

K2S

K2S3

KS2

Potassium sulfide consists of potassium (K) and sulfur (S) ions. Potassium has a +1 charge, while sulfide has a -2 charge. To balance the charges, two potassium ions are needed for every sulfide ion, resulting in the formula K2S. This reflects the stoichiometry of the compound, ensuring electrical neutrality in the compound by having two positive charges from potassium balance the single negative charge from sulfide.

Explanation

Potassium sulfide consists of potassium (K) and sulfur (S) ions. Potassium has a +1 charge, while sulfide has a -2 charge. To balance the charges, two potassium ions are needed for every sulfide ion, resulting in the formula K2S. This reflects the stoichiometry of the compound, ensuring electrical neutrality in the compound by having two positive charges from potassium balance the single negative charge from sulfide.

2. Which method is commonly used to determine the chemical formula of an ionic compound by swapping the absolute values of the charges as subscripts?

Stock method

Oxidation method

Criss-cross method

Lewis method

The Criss-cross method is a straightforward technique for determining the chemical formula of ionic compounds. It involves taking the absolute values of the charges of the cations and anions and using them as subscripts for the opposing ion. This ensures that the overall charge of the compound is neutral. For example, if a cation has a charge of +2 and an anion has a charge of -3, the formula is derived by placing a 3 as a subscript for the cation and a 2 for the anion, resulting in the formula being written as \( \text{A}_3\text{B}_2 \).

Explanation

The Criss-cross method is a straightforward technique for determining the chemical formula of ionic compounds. It involves taking the absolute values of the charges of the cations and anions and using them as subscripts for the opposing ion. This ensures that the overall charge of the compound is neutral. For example, if a cation has a charge of +2 and an anion has a charge of -3, the formula is derived by placing a 3 as a subscript for the cation and a 2 for the anion, resulting in the formula being written as \( \text{A}_3\text{B}_2 \).

3. What is the chemical formula of cobalt(III) fluoride?

CoF2

Co3F

CoF3

Co2F3

Cobalt(III) fluoride indicates that cobalt has a +3 oxidation state. In this state, cobalt can bond with fluoride ions, which each have a -1 charge. To balance the +3 charge of cobalt, three fluoride ions are required. Thus, the formula for cobalt(III) fluoride is CoF3, reflecting one cobalt ion paired with three fluoride ions to achieve electrical neutrality.

Explanation

Cobalt(III) fluoride indicates that cobalt has a +3 oxidation state. In this state, cobalt can bond with fluoride ions, which each have a -1 charge. To balance the +3 charge of cobalt, three fluoride ions are required. Thus, the formula for cobalt(III) fluoride is CoF3, reflecting one cobalt ion paired with three fluoride ions to achieve electrical neutrality.

4. The ionic compound (NH₄)₂SO₃ is named ____.

The ionic compound (NH₄)₂SO₃ consists of ammonium ions (NH₄⁺) and sulfite ions (SO₃²⁻). When naming ionic compounds, the cation (positive ion) is named first, followed by the anion (negative ion). In this case, "ammonium" refers to the cation, and "sulfite" refers to the anion derived from sulfur. Therefore, the compound is named ammonium sulfite, reflecting the composition of its constituent ions.

Explanation

The ionic compound (NH₄)₂SO₃ consists of ammonium ions (NH₄⁺) and sulfite ions (SO₃²⁻). When naming ionic compounds, the cation (positive ion) is named first, followed by the anion (negative ion). In this case, "ammonium" refers to the cation, and "sulfite" refers to the anion derived from sulfur. Therefore, the compound is named ammonium sulfite, reflecting the composition of its constituent ions.

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5. Ionic compounds must have a net charge of zero because they are electrically neutral.

True

False

Ionic compounds are formed by the electrostatic attraction between positively charged cations and negatively charged anions. For these compounds to be stable, the total positive charge must balance the total negative charge, resulting in a net charge of zero. This electrical neutrality is crucial for the formation of a stable ionic lattice structure, ensuring that the compound remains intact and does not dissociate into charged particles. Therefore, the statement that ionic compounds must have a net charge of zero is true.

Explanation

Ionic compounds are formed by the electrostatic attraction between positively charged cations and negatively charged anions. For these compounds to be stable, the total positive charge must balance the total negative charge, resulting in a net charge of zero. This electrical neutrality is crucial for the formation of a stable ionic lattice structure, ensuring that the compound remains intact and does not dissociate into charged particles. Therefore, the statement that ionic compounds must have a net charge of zero is true.

6. Match each ionic compound formula with its correct name.

CaS

NaCl

Mn₂O₃

Cr(NO₃)₃

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7. Which of the following correctly describes how binary acids are named?

Add the suffix -ate to the stem name of the element

Add the prefix hydro- and the suffix -ic to the stem name of the element

Add the suffix -ite to the stem name of the element

Add the prefix hypo- and the suffix -ous to the stem name of the element

Binary acids are named by adding the prefix "hydro-" to the stem name of the nonmetal element and the suffix "-ic." This naming convention applies to acids formed from two elements, typically hydrogen and a nonmetal. For example, HCl is named hydrochloric acid, where "chlor" is the stem from chlorine. This approach helps distinguish binary acids from oxyacids, which have different naming rules.

Explanation

Binary acids are named by adding the prefix "hydro-" to the stem name of the nonmetal element and the suffix "-ic." This naming convention applies to acids formed from two elements, typically hydrogen and a nonmetal. For example, HCl is named hydrochloric acid, where "chlor" is the stem from chlorine. This approach helps distinguish binary acids from oxyacids, which have different naming rules.

8. Which of the following statements about ionic bond formation are correct?

Ionic bonds are formed through electron transfer between atoms

Ionic bonds are stabilized by electrostatic forces of attraction

Ionic bonds are formed when two nonmetals share electrons equally

A cation is formed when an atom loses one or more electrons

Ionic bonds occur when one atom transfers electrons to another, resulting in the formation of charged ions. This electron transfer typically happens between a metal and a nonmetal, where the metal loses electrons to become a positively charged cation, while the nonmetal gains those electrons to become a negatively charged anion. The resulting cations and anions are held together by strong electrostatic forces of attraction, which stabilize the ionic compound. The statement about nonmetals sharing electrons describes covalent bonding, not ionic bonding.

Explanation

Ionic bonds occur when one atom transfers electrons to another, resulting in the formation of charged ions. This electron transfer typically happens between a metal and a nonmetal, where the metal loses electrons to become a positively charged cation, while the nonmetal gains those electrons to become a negatively charged anion. The resulting cations and anions are held together by strong electrostatic forces of attraction, which stabilize the ionic compound. The statement about nonmetals sharing electrons describes covalent bonding, not ionic bonding.

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