Screencast 27.1
www.youtube.com/watch?v=-iK8rzNlmQM
This screencast walks you through the use of bond enthalpies to predict the structure of phosphorus.

Screencast 27.2
www.youtube.com/watch?v=LMrTmVtMx3Q
This screencast walks you through the fluxionality of PF5.

Screencast 27.3
www.youtube.com/watch?v=zqs5_Vx4wxQ
This screencast walks you through calculations to compare the stability of NF3 and NCL3.