The second energy level can hold total of 8 electrons.
Carbon has atomic number equal to 6. There are 2 electrons in the first energy level and rest of the 4 electrons are in the second energy level.
So only 4 are present in second energy level while it can hold total 8.
4 is half of 8. So the percentage of energy level filled is half of 100%, the answer is 50%.
Answer: 50%
