Ionic+Bonds

=**__Ionic Bond:__**=
 * An ionic Bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions.
 * Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a nonmetal.
 * Pure ionic bonding cannot exist: all ionic compounds have some degree of covalent bonding.

A bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.

A chemical bond in which one atom gives up an electron to another, forming two ions of opposite charge, and thus generating an electrical force that holds the atoms together. The atoms are thus held together by the attractive force between a positively and a negatively charged ion.


 * An ionic bond is typically formed between a metal and a non-metal.**

__Formation:__
Atoms that have only one or very few electrons in their valence shell are very vulnerable to losing them. If another atom comes along with lots of electrons in it's valence shell, but not quite enough to be complete, the other atom's lonely old electron will get snatched away to join the shell with lots of electrons, and make a complete electron shell. When this happens though, a discrepancy in charge is created. The atom that now has the extra electron it's not supposed to have has a more negative charge, and the atom that got its electron stolen has a more positive charge. As you know, opposites attract, and in this case they attract so strongly that they two atoms become bonded to together.

For example, what happens if you have Na(sodium) and S(sulfur) during an ionic bonding. Here is a simple way to figure it out. Sodium has one electron in the outside electron shell and sulfur has two empty "spaces." So, if sodium(metal) give sulfur(non-metal) the one electron, but sulfur has one space left so another sodium comes along and that sodium gives its electron to sulfur. Thus, sulfur has no spaces. The chemical formula is Na2S because Sodium was used twice.



Structure
[|Ionic compounds] in the solid state form lattice structures. The two principal factors in determining the form of the lattice are the relative charges of the ions and their relative sizes. Some structures are adopted by a number of compounds; for example, the structure of the rock salt [|sodium chloride] is also adopted by many [|alkali] halides, and binary oxides such as [|MgO].

Bond strength
For a solid crystalline ionic compound the [|enthalpy] change in forming the solid from gaseous ions is termed the [|lattice energy]. The experimental value for the [|lattice energy] can be determined using the [|Born-Haber cycle]. It can also be calculated using the [|Born-Landé equation] as the sum of the [|electrostatic potential energy], calculated by summing interactions between cations and anions, and a short range repulsive potential energy term. The electrostatic potential can be expressed in terms of the inter-ionic separation and a constant ( [|Madelung constant] ) that takes account of the geometry of the crystal. The [|Born-Landé equation] gives a reasonable fit to the lattice energy of e.g. sodium chloride where the calculated value is −756 kJ/mol which compares to −787 kJ/mol using the [|Born-Haber cycle]. [|[1]]

Comparison with covalent bonds
In an ionic bond, the atoms are bound by attraction of opposite ions, whereas, in a [|covalent bond], atoms are bound by sharing electrons to attain stable electron configurations. In covalent bonding, the [|molecular geometry] around each atom is determined by [|VSEPR] rules, whereas, in ionic materials, the geometry follows maximum [|packing] rules. Purely ionic bonds cannot exist, as the proximity of the entities involved in the bond allows some degree of sharing [|electron density] between them. Therefore, all ionic bonds have some covalent character. Thus, an ionic bond is considered a bond where the ionic character is greater than the covalent character. The larger the difference in [|electronegativity] between the two atoms involved in the bond, the more ionic (polar) the bond is. Bonds with partially ionic and partially covalent character are called [|polar covalent bonds]. For example, Na–Cl and Mg–O bonds have a few percent covalency, while Si–O bonds are usually ~50% ionic and ~50% covalent.