Chemical bond A mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together.

Why Bond? Potential energy is lowered More stable

Types of bonds Ionic Covalent metallic

Ionic bonding Bonding that results from the electrical attraction between large numbers of cations and anions.

Covalent bonding Results from the sharing of electrons pairs between two atoms.

Metallic bonding Bonding that results from the attraction between metal atoms and the surrounding “sea of electrons” –Delocalized electrons – electrons that freely move around; empty orbitals overlap, electrons very mobile making a “sea” of electrons

How can you tell if a bond is ionic or covalent? A bond is rarely purely ionic or covalent. Usually falls somewhere between the two extremes. Diatomic – covalent

electronegativity Measure of an atom’s ability to attract electrons. The degree to which bond is ionic or covalent depends on the difference in electronegativities.

How to do Look up the electronegativities of the atoms involved on a chart. Subtract the two numbers Find where they fall on the ionic- covalent scale.

Polar Polar – an unequal sharing of electrons that lends a molecule to be partially negative at one end and partially positive at another. Water is an example.

Reading the chart Values above 1.7 are ionic, the closer you are to 3.3 the more ionic. Values under 1.7 are covalent. –Values under 0.3 are nonpolar -covalent –Values between 1.7 and.3 are polar -covalent