Ionic Bond Notes
Ionic Bonds
- Ionic bonds form between atoms with significantly different electronegativities.
- The atom that loses electrons becomes a cation (positive ion), while the atom that gains electrons becomes an anion (negative ion).
- The ionic bond is the result of the electrostatic force of attraction between oppositely charged ions.
- Electrons are not shared in an ionic bond; they are transferred.
Electronegativity Difference
- For electron transfer to occur, the difference in electronegativity ($\Delta EN$) must be greater than 1.7 on the Pauling scale.
- Ionic bonds generally form between a metal and a nonmetal.
- Alkali and alkaline earth metals (Groups 1A and 2A) readily form ionic bonds with halogens (Group 7A or 17).
- Active metals loosely hold onto their electrons, whereas halogens are more likely to gain an electron to complete their valence shell.
Examples of Ionic Compounds
- Cesium chloride ($\Delta EN = 2.3$)
- Potassium iodide ($\Delta EN = 1.7$)
- Sodium fluoride ($\Delta EN = 3.1$)
Physical Properties of Ionic Compounds
- High melting and boiling points due to the strength of the electrostatic force between ions. The melting point of sodium chloride is 801^{\circ}C.
- Many ionic compounds dissolve readily in water and other polar solvents.
- Good conductors of electricity in the molten or aqueous state.
- In the solid state, ionic compounds form a crystalline lattice consisting of repeating positive and negative ions.
Crystalline Lattice Structure
- Arrangement that maximizes attractive forces between oppositely charged ions and minimizes repulsive forces between ions of like charges.