Ionic solids and electrical conductivity — evaluate the assertion–reason Assertion (A): Ionic solids, in general, have no electrical conductivity in the solid state. Reason (R): In ionic solids, electrons are tightly bound to the nuclei and are not free to move.

Introduction / Context:
Ionic crystals (e.g., NaCl) conduct electricity when molten or dissolved but not typically in the solid state. Distinguishing the correct reason requires recognizing which charge carriers are responsible for conduction in different phases.

Given Data / Assumptions:

• Solid, stoichiometric ionic lattice at ordinary temperature.
• No significant defect-mediated ionic conduction (fast-ion conductors are special cases).
• Conduction mechanisms: electrons/holes vs mobile ions.

Concept / Approach:
In solid ionic lattices, the ions are held rigidly at lattice sites; there are no free charge carriers able to drift under an electric field. Thus bulk solid ionic compounds are insulators. The statement about tightly bound electrons is true but does not explain the lack of conduction in the ionic solid: even if electrons are localized, molten ionic liquids conduct because ions are mobile. The key factor is ion mobility, not electron binding.

Step-by-Step Solution:
Accept A: solid ionic compounds generally do not conduct.Evaluate R: electrons are indeed localized in ionic bonds (true).Causation: lack of mobile ions in the solid lattice, not just electron localization, explains non-conduction.Therefore, A and R true, but R is not the correct explanation of A.

Verification / Alternative check:
Experimentally, NaCl(s) is an insulator, NaCl(l) conducts well via ions; this change cannot be explained by electron binding alone.

Why Other Options Are Wrong:
Declaring R false ignores electronic structure; claiming R as the correct explanation overlooks ion immobility as the real cause.

Common Pitfalls:
Assuming only electrons can carry current; forgetting ionic conductivity in melts and solutions.

Final Answer:
Both A and R are true but R is not correct explanation of A