Lone Pair Orientation

The H-bonding interactions between gaseous HF and other small molecules, showing how their lone-pairs dictate the shapes of the adducts formed. The HF molecule (shown as enlarged spheres) is oriented along the three-fold axis of NH₃, collinear with HCN, out of the HOH plane in its complex with H₂O, and off the HF axis in the (HF)₂ dimer.