Lecture #12, February 10, 1997
For transition metal ions, the electronic configuration sequence changes from [Ar] 4s2 3d1 (the 3d orbital is the last to fill) to [Ar] 3d (in which there are no 4s electrons.
The (optional) explanation for this flipping in the order of valence electron filling can be illustrated by assuming that Zeff increases by one when an electron is removed to form the positively charged ion.
We illustrate what happens in the case of the valence electron of Na in excited states vs that of Na+ in the same excited states. Note that the 4s orbital, more stable than the 3d in Na, is less stable than the 3d in Na+
The sequence of steps (to date) for determining molecular structures. (In the near future, the next step allows us to make predictions about molecular geometries.)
Formal charge defined with an example
Formal charge defined with the example continued
Rules for determining preferred Lewis structures using formal charge considerations
Rules for determining preferred Lewis structures using formal charge considerations (continued)
Examples of the "incomplete octet" as exceptions to the Octet Rule that are possible for Groups I-III of the periodic table, and most frequently with the lightest members, e.g. Li, Be and B
Odd electron molecules cannot ever completely satisfy the Octet Rule