He put iron with sulfur and oxygen and it had a few more errors and iron is a metal the other two are nonmetals
Hepta is seven and tetra is four, so option c is your answer
Answer: 5
Explanation: add up all the electrons and it will amount to 23. Arranging by the old model for electronic configuration, we have : 2, 8, 8, 5
The last number being 5 represent its valence electron