Why must reagent bottles be closed when not in use?

This drawing shows a human body system. what is the primary function of this body system?

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!

Which type of intermolecular attractions holds ammonia molecules together with other ammonia molecules?