In this week's content, we shifted our perspective from looking at molecules as two-dimensional objects to seeing their three-dimensional properties. We learned that their electron domain and molecular geometries affect their molecular polarity. In coming lessons, we will see the impact that molecular polarity has on other properties of molecules (such as boiling point, viscosity, surface tension, reactivity, etc.)
Watch this video for a demonstration of molecular polarity in action! Prior to the video, the plastic rod being used was rubbed against an animal fur to induce a charge on the surface. As the rod is then brought near a stream of flowing hexane (the liquid on the right), we observe no effect. However, when the charged rod is placed near a stream of flowing water, we see that the stream is bent to the side. This indicates an attraction of the water molecules to the charged rod. This attraction is due to the polar nature of water. Since the hexane did not respond, we see that the level of attractions/repulsions is very low.
We also learned more about bonding. The valence bond theory helps us to understand more about the three-dimensional shapes of molecules by providing a rationale for how those shapes come to be. It also helps to explain the property of resonance.