Solid chromium (II) reacts with oxygen gas to form solid Cro. What is this type of reaction?

How much energy is made when a pice of wood burns. how do you know

Stage in which a star’s outer layers have started to cool and grow outward?

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!