How many km are in 1.29 x 10-2 cm?

Compare and contrast physical changes with chemical changes.

Suppose you wanted to make 100 grams of water. what is the molar mass of water (h2o)?

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!