Rank the four gases (air, exhaled air, gas produced from the decomposition of h2o2, gas from decomposition of nahco3, in order of decreasing concentration of oxygen

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!