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.
Electron
An electron can be "bound" to the nucleus of an atom by the attractive Coulomb force. A system of one or more electrons bound to a nucleus is called an atom. If the number of electrons is different from the nucleus' electrical charge, such an atom is called an ion. 
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Electron [SEP] Atoms and molecules
An electron can be "bound" to the nucleus of an atom by the attractive Coulomb force. A system of one or more electrons bound to a nucleus is called an atom. If the number of electrons is different from the nucleus' electrical charge, such an atom is called an ion. The wave-like behavior of a bound electron is described by a function called an atomic orbital. Each orbital has its own set of quantum numbers such as energy, angular momentum and projection of angular momentum, and only a discrete set of these orbitals exist around the nucleus. According to the Pauli exclusion principle each orbital can be occupied by up to two electrons, which must differ in their spin quantum number.