Question: how many electron shells are present in carbon oxygen and nitrogen?
Answer: Carbon has 6 electrons --- 2 in the first shell, and 4 in the second shell (so four valence electrons). Nitrogen has 7 electrons --- 2 in the first shell, and 5 in the second shell (so five valence electrons). Oxygen has 8 electrons --- 2 in the first shell, and 6 in the second shell (so six valence electrons).