Chapter 7, Problem 41A

Interpretation Introduction

Interpretation: The pairs of elements that cannot form ionic compound needs to be determined.

Concept Introduction: An ionic compound is formed when a metal reacts with a non-metal. Here, metal is electron efficient and thus, loses electrons and 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.

Explanation of Solution

Reason for correct option/s:

Considering (c) sodium and sulfur. Here, sodium is metal and sulfur is non-metal. Sodium can lose 1 electron to form sodium ion $\left({\text{Na}}^{+}\right)$ and sulfur can gain 2 electrons to form sulfide ion $\left({\text{S}}^{2-}\right)$ . The ionic compound is formed when 2 sodium atoms bonded with 1 sulfur atom. Thus, the formula is ${\text{Na}}_{\text{2}}\text{S}$ . Therefore, sodium and sulfur can form an ionic compound.

Therefore, the correct answer is option (c).

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 (a) sulfur and oxygen. Here, both sulfur and oxygen are non-metals thus, they cannot form an ionic compound.

Considering (b) sodium and calcium. Here, both sodium and calcium are metals thus, they cannot form an ionic compound.

Considering (d) oxygen and chlorine. Here, both oxygen and chlorine are non-metals thus, they cannot form an ionic compound.

Therefore, option (a), (b) and (d) are incorrect options.