Question

what is the reason for mentioning electron symbol -1e0​

Answer 1

A short and simplified answer:

The electronic configuration of an atom determines the chemical reactions the atom can participate in, and determines the kinds of molecules that atoms can combine into to form more complicated substances.

More Info :

The electron is a subatomic particle, (denoted by the symbol

e− or β−), whose electric charge is negative one elementary charge.

[9] Electrons belong to the first generation of the lepton particle family,

[10] and are generally thought to be elementary particles because they have no known components or substructure.

[1] The electron has a mass that is approximately 1/1836 that of the proton.

============================

$\sf\red{Thank\:you!}$