Which is an example of a homogenous mixture?

What mass of carbon dioxide is produced from the complete combustion of 4.50×10−3 g of methane?

Which diagram shows the correct way to represent an ionic compound of magnesium oxide?

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!