Within a family: the atomic radius will increase as you go down. why?

What element breaks down into yttrium-90?

The number at the end of an isotope’s name is the number.

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!