How many molecules are in 0.25 mole of CO?

What shape would a molecule with two bound groups and two lone pairs have?

How many grams of magnesium metal will react completely with 8.3 liters of 5.5m hcl? show all work

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!