In aqueous solutions, ionic compounds tend to dissociate into their constituent ions more readily than molecular compounds. This behavior stems from the nature of ionic and covalent bonds and their interactions with water molecules.
Ionic bonds are formed between atoms with significantly different electronegativities, resulting in a transfer of electrons from one atom to another. When ionic compounds are placed in water, the polar water molecules surround the individual ions. The positive end of water molecules attracts the negatively charged ions, while the negative end of water molecules attracts the positively charged ions. This interaction effectively pulls the ions apart, leading to dissociation.
On the other hand, covalent bonds involve the sharing of electrons between atoms. These bonds are typically stronger due to the stable electron pairs they create. When molecular compounds are added to water, although some may interact with water, many do not dissociate into individual atoms. Instead, they remain intact as whole molecules because the attractive forces that hold the covalent bonds together are generally stronger than the interactions between the covalent compound and water. As a result, covalent compounds tend to exist as whole units, while ionic compounds disassociate due to the strong solvation effects of water.
In summary, the difference in stability between ionic and covalent bonds in aqueous solutions is largely due to the nature of their bonds, the interactions with water, and the ability of ionic compounds to dissociate into ions under the influence of polar solvents like water.