ajv said:
Ok so if an electron is not being measured in any way shape or form, is it an extended object/ excitation?
Electrons (whether measured or not) are almost always extended objects. For the notion of a localized electron is a semiclassical concept that, strictly speaking, makes sense only at sizes bigger than its Compton wavelength. At smaller distances, the intuitive imagination associated with the particle concept breaks down completely, and the only right description is in terms of quantum field theory.
The theory of electrons is called QED (quantum electrodynamics). In QED, there is an electron field and an electromagnetic field. The electron field describes the properties associated semiclassically with electrons and positrons. But the correspondence is not simple. For example, there are no operators associated with single electrons. In particular, there is no position operator in QED. Thus one cannot meaningfully say that ''this electron moves from here to there', not even on the level one is used for a quantum mechanical particle (i.e., with a probability distribution on histories).
But there are operators for the charge density - so this is a concept that makes sense at any length scale. Therefore one can consistently talk about the charge density of the electron field, and indeed it is this charge density that is displayed by atomic microscopes. It is also the key quantity relevant in quantum chemistry, where the electron field is responsible for the binding of atoms.
Since the charge is quantized, there is also a notion of particle number (actually electron number minus positron number). But this is a global quantity, obtained by integrating the charge density over all of space at any particular time. (Which time does not matter as charge is conserved). It is this number that bridges the gap to the electron picture. For in case that a small volume contains an elementary charge, i.e., an electron field corresponding to the charge of a single electrons, and this small volume is reasonably closed in the sense that its interaction with the rest of the universe can be well approximated by an external potential then one can describe the system approximately by single-particle quantum mechanics (i.e., the Dirac or Schroedinger equation). This may apply to single electrons emitted by a source (cathode rays), to the outermost electron in an atom, or to a valence electron of an atom in an ion trap. These are the
only cases where one may consider an electron to be (approximately) well localized.
Already the case of two elementary charges is much more complicated. It gives rise to delocalized 2-electron superpositions making up simple bonds between atoms. The only natural intuitive description is then that of the charge density, i.e., an electron cloud. Multiple bonds involve even more charges, and again the charge density and the electron cloud are then natural ways to think about these on an intuitive level.
