Ca(hco3)2 molecular formula calculated

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!

What if it is did darwin used to support his theory of evolution

What is the empirical formula of a compound that is 50.7% antimony and 49.3% selenium ?