Final answer:
Bonding in ionic substances like NaCl involves the transfer of electrons and the formation of charged ions held together electrostatically, which is different from the shared electrons in covalent bonds seen in water.
Step-by-step explanation:
Bonding in molecular substances like water (H₂O) is covalent, where atoms share electrons to fill their valence shells. In contrast, ionic bonds, such as those in sodium chloride (NaCl), involve the complete transfer of electrons from one atom to another, resulting in the formation of charged ions. These ions are held together by electrostatic forces rather than sharing electrons.
In a covalent bond, the electrons tend to be shared equally when the bond is between identical atoms, as in Cl₂. If the atoms are different, as in H₂O, the sharing is unequal, with the electrons spending more time closer to one atom, creating a polar molecule with a slight charge difference across the molecule. This distinction is seen with water's hydrogen and oxygen atoms; the electrons are drawn more towards oxygen due to its higher electronegativity, resulting in a polar covalent bond.
When ionic compounds like NaCl are added to water, they dissociate into ions. The Na+ and Cl- ions are surrounded by spheres of hydration due to the polar nature of water. The positive region of water, the hydrogen atoms, attracts the negative chloride ions, while the negative region, the oxygen atom, attracts the positive sodium ions. This behavior is different from covalent compounds, which do not dissociate into ions in water but may form individual molecules when dissolved.