Properties Affected by Polarization:

Covalent character increases.
Lattice energy decreases (generally, as covalent character increases, the ionic contribution to lattice energy decreases).
Melting point decreases.
Hardness decreases.
Solubility in polar solvent decreases, in non-polar solvent increases.
Electrical conductivity decreases (in molten state or solution, due to less free ions).
Intensity of colour increases (e.g., ZnS (white) $\rightarrow$ CdS (yellow) $\rightarrow$ HgS (black)).
Acidic nature of oxides increases.
Thermal stability generally decreases (for compounds like carbonates, hydroxides, nitrates).
Volatility increases.

3.25 Melting Point of Ionic Compounds (Ionic Compounds ka Melting Point)

Melting point lattice energy aur polarization par depend karta hai.

When Polarization is Negligible: (Small anions like F$^-$, O$^{2-}$)
- Melting point order lattice energy order ko follow karta hai.
- Lattice energy ($U$) $\propto z^+z^- / r_0$.
- Example: NaF < MgO < ScN < TiC (melting point and lattice energy increase with charge).
- Example: BeO > MgO > CaO > SrO > BaO (melting point and lattice energy decrease with increasing $r_0$).
When Polarization is Dominating:
- Polarization badhne se melting point decrease hota hai.
- Example: NaX < MgX$_2$ < AlX$_3$ (covalent character badhne se melting point decrease).
- Example: MF > MCl > MBr > MI (F$^-$ ki polarizability kam, I$^-$ ki zyada).

3.26 Solubility of Ionic Compounds (Ionic Compounds ki Ghulansheelta)

Solubility lattice energy, hydration energy, polarization, etc. par depend karti hai.

Hydration Energy ($\Delta H_{hyd}$): Ion jab water mein dissolve hota hai, toh energy release hoti hai.

Dissolution Process: MX$_{(s)}$ $\rightarrow$ M$_{(g)}^{n+}$ + X$_{(g)}^{m-}$ ($\Delta H_{lattice}$ = -U) then M$_{(g)}^{n+}$ + X$_{(g)}^{m-}$ $\rightarrow$ M$_{(aq)}^{n+}$ + X$_{(aq)}^{m-}$ ($\Delta H_{hyd}$).

Overall: MX$_{(s)}$ $\rightarrow$ M$_{(aq)}^{n+}$ + X$_{(aq)}^{m-}$ ($\Delta H_{sol}$ = $\Delta H_{lattice}$ + $\Delta H_{hyd}$)

For solubility, $\Delta G_{sol} = \Delta H_{sol} - T\Delta S_{sol}$ should be negative. Generally, $\Delta H_{sol}$ should be negative for good solubility.

When Polarization is Dominating:
- Polar solvent mein, polarization badhne se solubility kam hoti hai (e.g., AgF > AgCl > AgBr > AgI).
- Non-polar solvent mein, covalent character badhne se solubility badhti hai (e.g., NaCl < NaI).
When Lattice Energy and Hydration Energy are Dominating:
- Agar cation ka size small ho, toh hydration energy dominant hoti hai, solubility badhti hai (e.g., LiClO$_4$ > NaClO$_4$).
- Agar anion ka size small ho, toh lattice energy dominant hoti hai, solubility kam hoti hai (e.g., LiF < NaF < KF < RbF < CsF).
- Exceptions: LiF (lattice energy high), NaI (polarization high).

3.27 Electrical Conductivity and Colour (Bijli aur Rang)

Electrical Conductivity:

Polarization badhne se covalent character badhta hai, ionisation tendency kam hoti hai, isliye electrical conductivity decrease hoti hai (e.g., LiCl > BeCl$_2$ in molten state).

Colour:

Polarization badhne se ionic compounds ka colour intensity badhti hai (e.g., AgCl (colourless) $\rightarrow$ AgI (yellow)).
Ye charge transfer transitions ki wajah se hota hai.

3.28 Acidic Nature of Oxides (Oxides ka Acidic Nature)

Polarization badhne se oxides ka acidic nature bad