Chapter 7, Problem 40A

Interpretation Introduction

Interpretation: The pairs of atoms that can form an ionic compound need to be determined.

Concept Introduction: An ionic compound is formed when a metal reacts with a non-metal. Here, metal is electron efficient and loses electrons while non-metal is electron deficient, thus, it gains electrons. In an ionic compound, metal has a partially positive charge and non-metal has a partially negative charge.

Answer to Problem 40A

Options (a), (c) and (e).

Explanation of Solution

Reason for correct option/s:

Considering Li and S, here, Li is a metal that can lose one electron to form lithium-ion ${\text{Li}}^{+}$ . Similarly, S is a non-metal which can gain 2 electrons to form sulphide ion ${\text{S}}^{2-}$ . Thus. 2 ${\text{Li}}^{+}$ ions can chemically combine with 1 ${\text{S}}^{2-}$ ion to form lithium sulphide ${\text{Li}}_{\text{2}}\text{S}$ .

Considering Al and O, here, Al is a metal that can lose 3 electrons to form an aluminumion ${\text{Al}}^{3+}$ . Similarly, O is a non-metal which can gain 2 electrons to form an oxide ion ${\mathrm{O}}^{2-}$ . Thus, 2 Al atoms combine with 3 O atoms to form aluminumoxide ${\mathrm{Al}}_2{O}_3$ .

Considering I and K. Here, I is non-metal which can gain 1 electron. K is a metal that can gain 1 electron. Thus, I and K both can combine to form an ionic compound KI.

Therefore, correct option is (a), (c) and (e).

Conclusion

Reason for incorrect option/s:

Ionic compounds are formed from metal and non-metal. Here, one atom (of metal) is electron rich which loses electron/s and one atom (of non-metal) is electron deficient which gains electron/s.

Considering O and S, here both O and S are non-metals thus, they cannot chemically combine to form an ionic compound.

Considering F and Cl. Here, both F and Cl are non-metals; thus, they cannot chemically combine to form an ionic compound.

Considering H and N. Here, both N and H are non-metals. They cannot combine chemically to form an ionic compound.

Therefore, options (b), (d), and (f) are incorrect options.