Work can BLANK energh between objects qnd can cause a change in form of energy

Why is retrograde motion an apparent motion

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!

To find the enthalpy of a reaction in the lab, you measured the of the reactants and the change during the reaction.