2KClO3 --> 2KCl + 3O2 How many moles of KClO3 are needed to produce 480 grams of O2?

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!

#20 which type of bond is formed when bases pair in dna? ionic bond covalent bond coordinate bond hydrogen bond

The image shows the process of which is used in nuclear power plants. photo attached