Question: how many electrons are in the outer subshell of a neutral oxygen atom?
Answer: Oxygen is #8 in the periodical table. First electron shell can hold 2 electrons; second, 8. Therefore, out of 8 electrons, 2 go to the first shell and 6 to the second; valence electrons are the ones on the outermost shell (there are some exceptions, but they are much further down the table).