# What types of elements make up ionic compounds?

Jul 8, 2017

Elements with differences of electronegativity of 2.0 or more.

#### Explanation:

Generally ionic compounds are formed from metallic elements with low electronegativity with nonmetals that have a high electronegativity.

Jul 8, 2017

Usually, ionic compounds are composed or metals, and non-metals........Why?

#### Explanation:

Metals, all metals, are electron-rich materials. $\text{Metallic bonding}$ by definition is $\text{positive ions in an electron sea}$. Metals thus TEND to form positive ions.........i.e. they are reducing.......

$M \left(s\right) \rightarrow {M}^{+} + {e}^{-}$

Such a bonding picture can account for common metallic properties: $\text{malleability}$, the ability to be hammered out into a sheet; $\text{ductility}$, the ability to be drawn out into a wire, and $\text{electrical conductivity}$ in the solid state.

On the other hand, non-metals, tend to derive from the right hand side of the Periodic Table, and their high (unshielded!) nuclear charge means that they tend to be highly oxidizing, (and thus tend to be reduced):

$\frac{1}{2} {O}_{2} \left(g\right) + 2 {e}^{-} \rightarrow {O}^{2 -}$..........or

$\frac{1}{2} C {l}_{2} \left(g\right) + {e}^{-} \rightarrow C {l}^{-}$

The positive and negative ions can of course pair up to form stable salts in which anion is bound to cation in an infinite, non-molecular array..........

$N a \left(g\right) + \frac{1}{2} C {l}_{2} \left(g\right) \rightarrow N a C l \left(s\right)$

And thus the elements that commonly make up ionic compounds are metals and non-metals...........