When will a salt become less soluble in water?

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!

Ahelium balloon contains 16.9 l of helium at stp. how many atoms of helium are in the balloon

Amethod of separation that employs a system with two phases of matter, a mobile phase and a stationary phase, is called