What is the maxlmum number of electrons that can be present in each principal energy level of hydrogen?

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.

Ibelieve y y even though i've only taken chemistry for one year