Ionic+Bonding

Ionic Bonding
An Ionic bond is created when two ions of separate charges, usually a metal cation and a nonmetal anion (excluding noble gases), are bonded due to the electrostatic attraction between them. One or more electrons from the metal, making a cation, will be transferred to the nonmetal, making an anion, and the forces between them will make a bond. The number of electrons donated will depend on the cation, it will keep on donating electrons until it has a completed octet and is stable. The electrons transferred to the anion will also cause it to have a completed octet.

Energy in Ionic Compounds
Ionic bonds are exothermic, even though the the process of losing an electron is and endothermic reaction. This is because the gaining of an electron by the nonmetal is an exothermic reaction and when the bond is created, energy is released. Energy is released because the ions of different charges attracted to each other, which stabilizes the compound. The attraction causes the ions to form a lattice, or a solid compound (shown below). These can be made up of an infinite amount of ions. Below is a compound of NaCl. Each sodium ion is attracted to the chlorine ions and every chlorine ion is attracted to a sodium ion, creating the alternate pattern in the solid. Because the solids can me made of an infinite amount of ions, Ionic compounds do not form single molecules.The lattice energy is the amount of energy required to break down a mole of a solid ionic compound into gaseous ions. Lattice energy increases as the charge of the ions increase and the radii decrease.



Example: forming NaCl
An electron is taken from the outer shell of the Sodium atom, making it stable completing the octet and becoming isoelectronic to Neon, and making it a cation. The electron goes to a Chlorine atom, also making it stable by completing the octet and becoming isoelectronic to Argon, and making it an anion. The electrostatic forces between the ions cause them the form a bond, creating NaCl.

Transition metals
Since ionization energy increases with every electron removed, lattice energies are usually only big enough to handle the loss of 3 electrons from a single atom. Most transition metals, however, require more than three electrons in order to achieve a noble-gas core, and usually do not form ions with noble-gas cores. Therefore, the octet rule does not apply to transition metals. Also, in forming ions, transition metals lost electrons from the s orbital first, then the proper amount from the d orbitals to reach the required charge.

example: For Fe ( [Ar] 4s2 3d6) to form Fe 2+, the atom would lose the two electrons from the 4s orbital, not the 3d. The electron configuration for Fe 2+ is [Ar] 3d6.

Common characteristics of Ionic compounds:

 * Form between metals and nonmetals.
 * Dissolve easily in water and have polar solvents.
 * Easily conduct electricity in solution.
 * Size of the metal decreases, size of the nonmetal increases
 * Form crystalline solids with high melting points.

Sources: http://www.3dchem.com/inorganics/NaCl-poly.jpg http://www.langara.bc.ca/biology/mario/Assets/ionbond.jpg http://www.visionlearning.com/library/module_viewer.php?mid=55 http://en.wikipedia.org/wiki/Crystal_structure AP Chem textbook