Ionic Bonding

Formation of an Ionic Bond and Ionic Compound Properties

Greetings,

This post will focus on the formation of an ionic bond and ionic compound properties.  Chemical bonds are the forces that hold atoms together.  In every case, electrostatic forces are involved, but there are different ways in which the bonds are formed.  We'll look at ionic bonding; how it happens and properties of the resulting crystalline structures.  To begin, study the following diagram.

Ion Formation - A Spontaneous Process

The transfer of an electron is a spontaneous process because it results in ions with a stable octet.  The stable octet is the condition resulting from an atom/ion acquiring a valence shell (highest energy) consisting of eight electrons.  An atom or ion with a stable octet of electrons has the same exact electron-configuration as the nearest noble gas on the Periodic Table!  Sodium ion has the same electron configuration (is isoelectronic with) as neon.  Chloride ion is isoelectronic with argon.  

Ionic Compound Crystal Formation

The diagram shows the transfer of an electron from an atom of sodium to an atom of chlorine to produce the ionic form of those elements.  Of course, there are very many ions produced from very many sodium and chlorine atoms.  Immediately, sodium and chloride ions "stick together" because oppositely charges attract: Ionic bonds have just been formed.  The ionic bonding process continues and a sodium chloride salt crystal is produced.  The sodium and chloride ions come together in an alternating 3-dimensional pattern.  At the atomic scale, a crystal of sodium chloride resembles a tiny cube and the shape is reproduced very many times until we are able to see cube-shaped crystals!

Properties of Ionic Compounds

Overall, the ionic bonds holding an ionic crystal together are incredibly strong.  The strength of these attractions makes it "difficult" to remove ions from the crystal.  Very high temperatures are required to begin removal of ions from the solid crystal; which must occur in order for a solid ionic compound to melt.  A strong charge-solvating liquid, like water, is required to dissolve ionic compounds.  The properties of ionic compounds is summarized below.

That's all for this post.  In my next post, we'll explore covalent bonding!