What could the fourth quantum number of a 3p3 electron be?

The answer to that would be magnesium

Yes it would be a physical change.

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.