how do you determine how many electrons are in the highest occupied energy level? For example many electrons are in the highest occupied energy level Group 3A
Count them up. For example, you know 1s2, 2s2, 2p6, 3s2, 3p6, etc etc. You can go to www.webelements.com and click on the pro edition, then scroll down the left side menu to electron configuration and get any element you wish.