Not True for Ionic Compounds:

Introduction:
Ionic compounds are formed by the transfer of electrons between atoms. They consist of positively charged ions (cations) and negatively charged ions (anions) held together by electrostatic attractions. Ionic compounds have unique properties that distinguish them from covalent compounds.

Explanation:

1. Ionic bond is non-directional:
The first statement is true. Ionic bonds are non-directional, meaning that the electrostatic attraction between ions occurs in all directions. This is because the positive and negative charges are evenly distributed throughout the compound. Unlike covalent bonds, which are directional and involve the sharing of electrons between specific atoms, ionic bonds involve the transfer of electrons between atoms.

2. Ionic compounds have higher melting points:
The second statement is true. Ionic compounds generally have higher melting points than covalent compounds. This is due to the strong electrostatic forces of attraction between the ions in the crystal lattice of the ionic compound. These forces require a significant amount of energy to overcome, resulting in a higher melting point. In contrast, covalent compounds have weaker intermolecular forces and therefore lower melting points.

3. Ionic compound does not exist as molecules:
The third statement is true. Ionic compounds do not exist as discrete molecules. Instead, they form a crystal lattice structure in which the positive and negative ions are arranged in a repeating pattern. This is because the ionic bonds extend throughout the entire crystal structure, rather than being localized between specific atoms.

4. Not all ionic compounds are soluble in water:
The fourth statement is not true. Not all ionic compounds are soluble in water. The solubility of an ionic compound depends on the strength of the attractions between the ions in the compound and the water molecules. Compounds with strong attractions between ions and water molecules are soluble, while those with weak attractions are insoluble or only partially soluble.

Conclusion:
In summary, the statement that is not true for ionic compounds is that all ionic compounds are soluble in water. While many ionic compounds are soluble, not all of them exhibit this property. The solubility of an ionic compound depends on the strength of the attractions between its ions and water molecules.

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