who discovered that it has two charges?
French chemist Charles François du Fay
Electron
In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids
where are electrons found in an atom and what electrical charge and mass do they have An electron can be "bound" to the nucleus of an atom by the attractive Coulomb force.  If the number of electrons is different from the nucleus' electrical charge, such an atom is called an ion. which theory explains or is based on this? Atomic Theory, Quantum Theory what exactly is the part of the atom mentioned above, initially? The electron is a subatomic particle, whose electric charge is negative one elementary charge.
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Electron [SEP] Discovery of two kinds of charges
In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids, "vitreous" fluid from glass rubbed with silk and "resinous" fluid from amber rubbed with wool. These two fluids can neutralize each other when combined. American scientist Ebenezer Kinnersley later also independently reached the same conclusion. A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess (+) or deficit (−).