Point particle of point charges cannot be maintained in an equilibrium configuration solely by the electrostatic interaction of the charges. In quantum mechanics, there is a distinction between an elementary particle (also called "point particle") and a composite particle. An elementary particle, such as an electron, quark, or photon, is a particle with no internal structure. Whereas a composite particle, such as a proton or neutron, has an internal structure (see figure). However, neither elementary nor composite particles are spatially localized, because of the Heisenberg uncertainty principle. The particle wavepacket always occupies a nonzero volume. For example, see atomic orbital: The electron
Alan (given name) what is today Brittany, France. An early figure who bore the name was St Alan, a 5th-century bishop of Quimper. This saint became a cult figure in the Brittany during the Middle Ages. Another early bearer of the name was St Alan, a 6th-century Cornish saint, who has a church dedicated to his memory in Cornwall (for example see St Allen, a civil parish in Cornwall named after this saint). Today the use of the given name (and its variants) is due to its popularity among the Bretons who imported the name to England, to Cornwall, and later to Ireland.