Why did you post this again? Because you're lazy and wanted people to not see my post? Once again, ONE QUESTION AT A TIME. We're here to help you with a tough question or work you through it, not do all your homework.
Answer:
A phosphorus atom forms a P3- ion by gaining three electrons.
here
Answer:
What do you need please to understand?
Each correspond to a principal energy level
B - two hydrogen atoms and one oxygen atom
