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Partial ChargeA partial charge is a charge with an absolute value of less than one elementary charge unit. For example, an "up quark" has an intrinsic charge of +1/3 of a unit and a down quark has an intrinsic charge -2/3 of a unit. Besides these partial charges which exist in an absolute sense and which represent fundamental properties of certain matter particles, more arbitrary partial charges often are created when unit charges are distributed asymmetrically. The resulting partial charges are a property only of zones within the distribution, and not the assemblage as a whole. For example, chemists often choose to look at a small space surrounding the nucleus of an atom: When an electrically neutral atom bonds chemically to another neutral atom that is more "electronegative", its electrons are partially drawn away. This leaves the region about that atom's nucleus with a partial positive charge, and it creates a partial negative charge on the atom to which it is bonded. In such a situation, the distributed charges taken as a group always carries a whole number of elementary charge units. Yet one can point to zones within the assemblage where less than a full charge resides, such as the area around an atom's nucleus. This is possible in part because particles are not like mathematical points--which must be either inside a zone or outside it--but are smeared out by the uncertainty principle of quantum mechanics. Because of this smearing effect, if you define a sufficiently small zone, a fundamental particle may be both partly inside and partly outside it.
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