Page "Chemical bond" Paragraph 6

In a simplified view of an ionic bond, the bonding electron is not shared at all, but transferred.

In this type of bond, the outer atomic orbital of one atom has a vacancy which allows addition of one or more electrons.

These newly added electrons potentially occupy a lower energy-state ( effectively closer to more nuclear charge ) than they experience in a different atom.

Thus, one nucleus offers a more tightly bound position to an electron than does another nucleus, with the result that one atom may transfer an electron to the other.

This transfer causes one atom to assume a net positive charge, and the other to assume a net negative charge.

The bond then results from electrostatic attraction between atoms, and the atoms become positive or negatively charged ions.

Ionic bonds may be seen as extreme examples of polarization in covalent bonds.

Often, such bonds have no particular orientation in space, since they result from equal electrostatic attraction of each ion to all ions around them.

Ionic bonds are strong ( and thus ionic substances require high temperatures to melt ) but also brittle, since the forces between ions are short-range, and do not easily bridge cracks and fractures.

This type of bond gives a charactistic physical character to crystals of classic mineral salts, such as table salt.