Why is it important to know the number of valence electrons in an atom?

Zinc + lead(ii) nitrate yield zinc nitrate + leadwhat's the chemical equation for this?

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 of the following are in a chemical family a. ca, sc, k b. cu, ag, au c. so, ge, sb