a substance breaks down into its component elements when it is heated. if 68.0 grams of the substance is present before it is heated, what is the combined mass of the component elements after heating?

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!