The concentration of N2O5 was monitored over time as it decomposed. 2 N2O5 (g) → 4 NO2 (g) + O2 (g) At 300.0 s, the concentration of N2O5 was 2.50×10−2 M. At 800.0 s, the concentration of N2O5 had decreased to 1.55×10−2 M. Calculate the average rate of change of O2 over the time interval from t = 300.0 s to t = 800.0 s.

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!