Chapter 7.2, Problem 14LC

(a)

Interpretation Introduction

Interpretation: The correct chemical formula for a compound formed from potassium and sulfur needs to be determined.

Concept Introduction: The formula of an ionic compound is written in such a way that the symbol for metal is written first, followed by the symbol for non-metal. Also, the number of atoms of each element (metal or non-metal) is written on the subscript of the symbol of the atom of the respective element.

Answer to Problem 14LC

  ${\text{K}}_{\text{2}}\text{S}$

Explanation of Solution

The given elements are potassium and sulfur. Here, potassium belongs to group 1 thus, it has 1 valance electron. It can lose 1 electron to form potassium cation $\left({\text{K}}^{+}\right)$ . Similarly, sulfur belongs to group 16 thus, it has 6 valence electrons. It can gain 2 electrons to form a sulfur anion $\left({\text{S}}^{2-}\right)$ . Now, to form an ionic compound, potassium cation and sulfur anion must combine in a ratio such that the total charge is zero. Thus, 2 potassium cations combine with 1 sulfur anion to form ${\text{K}}_{\text{2}}\text{S}$ .

Thus, the formula of the compound will be ${\text{K}}_{\text{2}}\text{S}$

(b)

Interpretation Introduction

Interpretation: The correct chemical formula for the compound formed from calcium and oxygen needs to be determined.

Concept Introduction: The formula of an ionic compound is written in such a way that the symbol for metal is written first, followed by the symbol for non-metal. Also, the number of atoms of each element (metal or non-metal) is written on the subscript of the symbol of the atom of the respective element.

Answer to Problem 14LC

  $\text{CaO}$

Explanation of Solution

The given elements are calcium and oxygen Here, calcium belongs to group 2 thus, it has 2 valance electrons. It can lose 2 electrons to form calcium cation $\left({\text{Ca}}^{2+}\right)$ . Similarly, oxygen belongs to group 16 thus, it has 6 valence electrons. It can gain 2 electrons to form an oxygen anion $\left({\text{O}}^{2-}\right)$ . Now, to form an ionic compound, calcium cation and oxygen anion must combine in a ratio such that the total charge is zero. Thus, they combine in a 1:1 ratio to form $\text{CaO}$ .

Therefore, the formula of the compound will be $\text{CaO}$ .

(c)

Interpretation Introduction

Interpretation: The correct chemical formula for the compound formed from sodium and oxygen needs to be determined.

Concept Introduction: The formula of an ionic compound is written in such a way that the symbol for metal is written first, followed by the symbol for non-metal. Also, the number of atoms of each element (metal or non-metal) is written on the subscript of the symbol of an atom of the respective element.

Answer to Problem 14LC

  ${\text{Na}}_2\text{O}$

Explanation of Solution

The given elements are sodium and oxygen Here, sodium belongs to group 1 thus, it has 1 valance electron. It can lose 1 electron to form sodium cation $\left({\text{Na}}^{+}\right)$ . Similarly, oxygen belongs to group 16 thus, it has 6 valence electrons. It can gain 2 electrons to form an oxygen anion $\left({\text{O}}^{2-}\right)$ . Now, to form an ionic compound, sodium cation and oxygen anion must combine in a ratio such that the total charge is zero. Thus, they combine in a 2:1 ratio to form ${\text{Na}}_2\text{O}$ . Therefore, the formula of the compound will be ${\text{Na}}_2\text{O}$ .

(d)

Interpretation Introduction

Interpretation: The correct chemical formula for the compound formed from aluminum and nitrogen needs to be determined.

Concept Introduction: The formula of an ionic compound is written in such a way that the symbol for metal is written first, followed by the symbol for non-metal. Also, the number of atoms of each element (metal or non-metal) is written on the subscript of the symbol of the atom of the respective element.

Answer to Problem 14LC

  $\text{AlN}$

Explanation of Solution

The given elements are aluminum and nitrogen Here, aluminum belongs to group 13 thus, it has 3 valance electrons. It can lose 3 electrons to form an aluminum cation $\left({\text{Al}}^{3+}\right)$ . Similarly, nitrogen belongs to group 15 thus, it has 5 valence electrons. It can gain 3 electrons to form a nitrogen anion $\left({\text{N}}^{3-}\right)$ . Now, to form an ionic compound, aluminum cation and nitrogen anion must combine in a ratio such that the total charge is zero. Thus, they combine in a 1:1 ratio to form $\text{AlN}$ .

Therefore, the formula of the compound will be $\text{AlN}$ .