Alternative strategies to the one used in this chapter have been proposed for applying the VSEPR theory to molecules or ions with a single central atom. In general, these strategies do not require writing Lewis structures. In one strategy, we write 

(1) The total number of electron pairs = [(number of valence electrons) ± (electrons required for ionic charge)]/2

(2) The number of bonding electron pairs = (number of atoms) - 1

(3) The number of electron pairs around central atom = total number of electron pairs - 3 x [number of terminal atoms (excluding H)]

(4) The number of lone-pair electrons = number of central atom pairs - number of bonding pairs After evaluating items 2, 3, and 4, establish the VSEPR notation and determine the molecular shape. Use this method to predict the geometrical shapes of the following:

(a) PCl₅;

(b) NH₃;

(c) ClF₃;

(d) SO;

(e) ClF₄^-;

(f) PCl₄⁺.

Justify each of the steps in the strategy, and explain why it yields the same results as the VSEPR method based on Lewis structures. How does the strategy deal with multiple bonds?