...It's also helpful to recall that 3d orbitals fill in the 4th row's ten transition elements between the 4s and 4p 'bookend' slots. It was enjoyable to make the "final four" of the 21 high-school teams competing at the Corning, NY chapter of the American Chemical Society's May 1981 "Chem Bowl". Virginia Tech favored me with a full 1st-year of advanced-placement (AP) chemistry credits. (read more)