Editing Elementary charge (section)

=== Fractional elementary charge ===
There are two known sorts of exceptions to the indivisibility of the elementary charge: [[quark]]s and [[quasiparticle]]s.
* [[Quark]]s, first posited in the 1960s, have quantized charge, but the charge is quantized into multiples of {{nowrap|{{sfrac|1|3}}&thinsp;''e''}}. However, quarks cannot be isolated; they exist only in groupings, and stable groupings of quarks (such as a [[proton]], which consists of three quarks) all have charges that are integer multiples of ''e''. For this reason, either 1&nbsp;''e'' or {{nowrap|{{sfrac|1|3}} ''e''}} can be justifiably considered to be "the [[quantum]] of charge", depending on the context. This charge commensurability, "charge quantization", has partially motivated [[Grand Unified Theory#Motivation|grand unified theories]].
* [[Quasiparticle]]s are not particles as such, but rather an [[emergence|emergent]] entity in a complex material system that behaves like a particle. In 1982 [[Robert B. Laughlin|Robert Laughlin]] explained the [[fractional quantum Hall effect]] by postulating the existence of fractionally charged [[quasiparticle]]s. This theory is now widely accepted, but this is not considered to be a violation of the principle of charge quantization, since quasiparticles are not [[elementary particles]].