Lesson 8: 3.8 Representations of Solutions

How does water interact with an ionic compound during the process of dissolution?
How must the orientations of water molecules differ when surrounding a cation versus an anion?

Solvation Shell
Dissolution
Ion-Dipole
Hydration Sphere
Partial Charge

Learning Objective 3.8.A; Suggested Skill 1.1 (Models and Representations).

Focuses on drawing solvation shells. Water is a polar molecule with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms. When an ionic solid dissolves, the oxygen ends must orient toward the positive cations, and the hydrogen ends must orient toward the negative anions.

Support: Give students cut-out models of water molecules labeled with partially + and partially - symbols to physically arrange around paper ions before sketching.
Extension: Have students draw a particulate representation of a polar molecular solute (e.g., methanol) interacting with water, contrasting this with an ionic solute dissolution mechanism.

Solid magnesium chloride (MgCl2) dissolves completely in water. In the box provided, sketch a particulate diagram showing one Mg^2+ ion and one C^1- ion fully solvated by water molecules. Use at least 3 water molecules per ion, ensuring you represent the correct spatial orientation of the water molecules relative to each ion.