In the CBSE Class 10 Chemistry chapter 'Metals and Non-Metals', one of the most frequently asked, high-scoring board exam questions is about the physical properties of salt.
The question asks: "Give reasons why ionic compounds (like Sodium Chloride) generally have extremely high melting and boiling points."
Statement: Ionic compounds universally have high melting and boiling points.
Core Reason: Presence of incredibly strong Electrostatic Forces of Attraction between the positive and negative ions.
Structure: They form massive, tightly packed 3D crystalline lattice structures.
Energy Requirement: It takes massive amounts of thermal energy (heat) to break these strong ionic bonds.
Classic Example: Sodium Chloride (NaCl) melts at a massive 801°C.
Ionic compounds are formed by the complete transfer of electrons from a metal to a non-metal, creating massive, oppositely charged ions (like a positive Na⁺ cation and a negative Cl⁻ anion). Because opposite charges attract each other magnetically, these ions are locked together by incredibly strong, unbreakable Electrostatic Forces of Attraction. They do not exist as single molecules; they pack tightly together into a massive, rigid 3D crystal lattice. To melt this solid crystal into a liquid, you must violently break these massive electrostatic bonds apart. Breaking these ultra-strong magnetic bonds requires a massive amount of thermal heat energy.
To understand how strong this is, compare salt with a covalent compound like Wax or Butter. Wax is made of non-metals sharing electrons weakly. The force between wax molecules is very weak, so if you leave wax in the sun (low heat), it instantly melts. However, standard table salt (NaCl) requires an astonishing furnace temperature of 801°C just to melt into a liquid!
Ionic compounds have high melting points because their positive and negative ions are locked tightly together by incredibly strong electrostatic forces of attraction. It requires a massive amount of heat energy to break these strong bonds and melt the solid crystal.
They are held together by strong Electrostatic Forces of Attraction (the magnetic-like pull between a positive cation and a negative anion).
No. Covalent compounds (like water, oil, or wax) generally have very low melting and boiling points because the intermolecular forces holding them together are extremely weak.
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