What is the charge of an atom before any electrons are transferred?

The charge of an atom before any electrons are transferred is zero. An atom as a whole is electrically neutral.

An atoms contains same number of electrons and protons. The charge of an electron and a proton is equal in magnitude but opposite in sign. The charge of a proton is 1.6 x 10⁻¹⁹C and the charge of an electron is - 1.6 x 10⁻¹⁹C. Thus the charge of all the protons in an atoms is neutralized by the total charge of all the electrons. Thus an atom is electrically neutral.

when an atom loses electrons, it acquires a positive charge and when it gains electrons, it acquires a net charge.