Which type of substance ionizes completely and creates hydronium ions when dissolved in water?

What does the process of natural selection involve

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!

How much heat is added if 0.814g of water increase in temperature by 0.351 degree c?