Ionic bonding
When a substance contains atoms of both metals and nonmetals, the electrons are naturally more attracted to the nonmetals. The nonmetals become negatively charged ions and the metals naturally become positively charged ions. (NOTE: The number of electrons that is gained or lost by the nonmetal and the metal is determined by the Octet rule.) An attractive force exists between the oppositely charged ions. The force that keeps the ions held together is the chemical bond called the ionic bond.
Ionic bonding requires a transfer of electrons from a metal to a nonmetal, a process that forms ions. Once these ions are formed, they arrange themselves into a 3-dimensional crystal in the solid state.
Lewis electron dot symbols can be used to describe ionic bonding in:
Properties
Some general points can be made about ionic compounds:
- The smallest unit of an ionic compound is a formula unit. The mass of this formula unit is called the formula mass.
- The formula unit of sodium chloride is NaCl. It has a formula mass is 58.44 amu/formula unit.
- The formula unit of sodium chloride is MgCl2. It has a formula mass is 95.21 amu/formula unit.
- The strong attractions between the cations and the anions in ionic solids are responsible for their high melting points. For ionic compounds, melting points typically range from 300°C to 1000°C.
- Ionic compounds are soluble in water.
- In aqueous solution, an ionic compound dissociates into its ions.
- This means that when NaCl is dissolved in water, the solution contains Na+ ions and Cl- ions.
- The dissociated ions in aqueous solution gives the solution the ability to conduct electricity. Therefore, ionic compounds dissolved in water makes strong electrolytes.
Content suitability
BCIT courses: CHEM 0011
