Unit+2+-+Electronegativity+and+Polarity

__Electronegativity & Polarity__
 * [|Electronegativity] is a property of an atom; it defines the likelihood that an atom will attract and hold on to electrons.
 * Polar bonds occur when there is a difference in electronegatives between the atoms involved in a bond.
 * If one side of the molecule has a higher electronegativity it will accumulate a partial negative charge (the negative pole); the oppostie side of the molecule would have lost some electron density, giving it a partial positive charge.
 * Electronegativity can be found on your periodic table.

__ Significance of Polarity __
 * Polarity plays a role in the behaviour of molecules:
 * 1) Polar molecules are miscible (mixable) with other polar molecules.
 * 2) Non-polar molecules are miscible in other non-polar molecules.
 * 3) Polar molecules and non-polar molecules are not miscible. For example, oil and water: oil is a long hydrocarbon chain, completely surrounded by hyrdogen, where as water is s small polar molecule.
 * Polarity plays a role in how a molecule reacts to such stimulus as microwaves, polar molecules spin violently when exposed to microwaves, non-polar molecules do not.
 * For further information on [|Polarity.]

__Examples__ > > > > > __Hints__ media type="youtube" key="Kj3o0XvhVqQ&hl=en" height="344" width="425"
 * 1) H 2 O - oxygen has a higer electronegativity than hydrogen. This creates a partial negative charge on the oxygen; this additonal electron density arose because hydrogen gave up electrons to oxygen, giving hydrogen a partial positive charge. [[image:H2O.jpg align="center"]]
 * 1) CCl 4 i s a non-polar molecule; a tetrahedral molecule, carbon tetrachloride has the same atom (Cl) projected in every direction. Since Cl is more E.N. than C, the molecule will have the same charge in every direction, making the molecule non-polar.
 * If the moleucle's charges are the __same__ in every direction, it is __not polar__.
 * If the molecule's charges are __different__ in two directions, it is __polar__.
 * A video to help explain electronegativity:
 * Sample questions on discussion page!