Soap Bubbles and Bonding

The objective of this experiment is to demonstrate the concept of VESPR (valence-shell electron-pair repulsion model) in a fun experiment that can be performed in the laboratory, outside or at home. Multiple soap bubbles arrange themselves in beautiful space filling replicas of hybridized atomic orbitals. These multiple bubbles vividly demonstrate how the repulsive forces drive the geometric arrangement of orbitals or the arrangement of atoms around a central atom. The only equipment required for this experiment is either a commercial soap bubble solution (or one made with soap and glycerin) and a bubble blower device capable of creating multiple single bubbles at one time. The commercial devices are simple plastic hoops with fins to hold a greater quantity of soap solution.

The procedure for this experiment involves blowing a stream of medium sized bubbles and then joining them together to form the multiple bubbles. Joining the bubbles is obviously the challenging yet fun part of this experiment.

Load the bubble blower hoop with soap solution and steadily blow through the hoop to form multiple bubbles of similar size. The bubbles should be directed upwards to allow more time to catch them on the hoop.

Catch a bubble on the hoop and then catch a second bubble on the opposite side of the hoop.

Pull the hoop sideways away from the bubbles and a double bubble will float free. The shape of this double bubble very closely approximates a diatomic molecule.

Form a double bubble on the hoop and then catch a third bubble between the two on the hoop. The edge of the hoop will face this third bubble.

Carefully pull the hoop away from the bubbles and a trigonal planer arrangement of the three bubbles will be the result.

It is very easy to catch two bubbles and fairly easy to catch three bubbles. The challenge is the tetrahedron.  Form a triple bubble on the hoop and then attempt to catch a fourth bubble on the opposite side of the third bubble. When (or if) the fourth bubble is caught, the hoop can be pulled free resulting in a beautiful tetrahedral arrangement of the four bubbles.