FIGURE 2-7 Electrostatic interactions of the oppositely charged ions of salt (NaCl) in crystals and in aqueous solution. (a) In crystalline table salt, sodium atoms are positively charged ions (Na⁺) due to the loss of one electron each, whereas chloride atoms are correspondingly negatively charged (Cl^–) by gaining one electron each. (b) In solid form, ionic compounds form neatly ordered arrays, or crystals, of tightly packed ions in which the positive and negatively charged ions counterbalance each other. (c) When the crystals are dissolved in water, the ions separate, and their charges, no longer balanced by immediately adjacent ions of opposite charge, are stabilized by interactions with polar water. The water molecules and the ions are held together by electrostatic interactions between the charges on the ion and the partial charges on the water’s oxygen and hydrogen atoms. In aqueous solutions, all ions are surrounded by a hydration shell of water molecules.