Question

can a -ve charge like a electron be present on its own in free space without any +ve or a neutral charge.......

Answer 1

an electron cannot be isolated by t has -ve charge (attractive forces)tends to attract other bodies
http://www.bourbaphy.fr/gabrielse.pdf
here they say that electron isolation is possible/(one more thing if the isolated electron
has any other charge than negative,then would it be called an isolated electron anymore?)

Answer 2

Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space (either a volume or an area) rather than distinct point-like charges. This model typically applies when charge carriers have been emitted from some region of a solid—the cloud of emitted carriers can form a space charge region if they are sufficiently spread out, or the charged atoms or molecules left behind in the solid can form a space charge region. Space charge usually only occurs in dielectric media (including vacuum) because in a conductive medium the charge tends to be rapidly neutralized or screened. The sign of the space charge can be either negative or positive. This situation is perhaps most familiar in the area near a metal object when it is heated to incandescence in a vacuum. but space charge is a significant phenomenon in many vacuum and solid-state electronic devices.

Answer 3

Physical explanation
When a metal object is placed in a vacuum and is heated to incandescence, the energy is sufficient to cause electrons to "boil" away from the surface atoms and surround the metal object in a cloud of free electrons. This is called thermionic emission. The resulting cloud is negatively charged, and can be attracted to any nearby positively charged object, thus producing an electrical current which passes through the vacuum.
Space charge can result from a range of phenomena, but the most important are:
Combination of the current density and spatially inhomogeneous resistance
Ionization of species within the dielectric to form heterocharge
Charge injection from electrodes and from a stress enhancement
Polarization in structures such as water trees

Answer 4

The short answer is yes. Free electrons can and do exist and need not be paired with other matter, whether it be of negative or neutral charge.

This is in contrast with magnetism, where a "north pole" of a magnet (we currently have good reasons to believe) can not exist independently in space free of a "south pole".