If I understand it right, an acceptor atom is that one which accepts the electrons, then it

has positive charge and thus it is able to attract the negatively charged electrons.

O2

ADDED:

Not O2, but one atom of oxygen.

If an acceptor atom is placed in a pure semiconductor, it will accept one or more electrons from the valence band of the semiconductor. This will permit positive holes in the conduction band to carry electrical current - the overall result is that the material will behave as a p-type semiconductor.

Bromine is an acceptor of electrons

Donor atoms are those impurity atoms in a semiconductor material that give free electons to the material, for example a 5-valent atom in a semiconductor consisting of 4-valent atoms. Acceptor atoms are 3-valent atoms in a 4-valent semiconductor, so an acceptor atom can "accept" an electron from the surrounding atoms what leaves a free "hole" . Free electrons (from donor atoms) and free holes (from acceptor atoms) make the semiconductor conduct electricity.