Fill in the blanks to determine the number of protons and electrons in an oxygen ion. (consult the periodic table to determine the number of protons in a neutral oxygen atom.) the o2− ion has protons and electrons.

When we consult periodic table, we see that neutral oxygen atom have eight protons and eight electrons. the ion O2- has eight protons and ten electrons.
Because the charge of ion shows that it gains two electrons, so before it was 8 electrons and after gaining 2 electrons it will be 10 electrons.
if an element gains electrons, it is negatively charged and when it loses electrons it is positively charged, proton always the same.

They are all full and don't need any more electrons in there outer shell.