7A elements are the halogens, which are in the 17th column of the periodic table. Here's how to determine the number of electrons in their highest energy level:

* Valence Electrons: Elements in the same column have the same number of valence electrons (electrons in the outermost energy level). Halogens have 7 valence electrons.

* Highest Occupied Level: The highest occupied energy level is the same as the period number the element is in. For example, fluorine (F) is in period 2, so its highest occupied energy level is 2.

Therefore, all 7A elements have 7 electrons in their highest occupied energy level.