An electron is a subatomic particles of spin 1/2. It couples
with photons and, thus, is electrically charged. It is a lepton
with a rest mass of 9.109 * 10 − 31kg and an electric charge of
− 1.602 * 10 − 19 C, which is the smallest known charge possible
for an isolated particle (confined quarks have fractional
charge). The electric charge of the electron e is used as a unit
of charge in much of physics. Electron pairs within an orbital
system have opposite spins due to the Pauli exclusion principle;
this characteristic spin pairing allows electrons to exist in
the same quantum orbital, as the opposing magnetic dipole
moments induced by each of the electrons ensures that they are
attracted together. Current theories consider the electron as a
point particle, as no evidence for internal structure has been
observed. As a theoretical construct, electrons have been able
to explain other observed phenomena, such as the shell-like
structure of an atom, energy distribution around an atom, and
energy beams (electron a