Zareh Darakjian Ph.D. Sep 17, 2008:

shell It seems to me now, that one possibleity, closer in meaning, is "shell electrons". Electrons move in "shells", which are paths of motion. Shell electrons are both of core and valence type. The nucleus is surrounded by both core and valence electrons which make up the shell electrons.

Zareh Darakjian Ph.D. Sep 17, 2008:

Question It seems that Dr. Frankland's answer is correct. I would like to know, if you can help me, how come "cortical" means exactly the oppostite "core". To my knowledge, core is the inner part and cortical, the outer one. In chemistry, the outer electrons are the "valence electrson". The inner ones the "core electrons".