The number of electrons in the outer electron layer of an atom, the nucleus of which contains 8 protons, is …

All known chemical elements are included in the list known as the “Periodic Table”. According to the general rule known in chemical science, each of the atoms of any chemical element contains the number of protons and electrons equal to the ordinal number of the chemical element in the periodic table. Therefore, in accordance with the condition of the problem, the considered chemical element is oxygen, and the number of electrons located in the outer electron layer of the atom is equal to the number of protons, i.e. eight.