When it comes to learning the basics of chemistry, many people often do not appreciate how these concepts can be applied to research (Puigdollers, Schlexer, & Pacchioni, 2015). Recently in class in chapter 6 we learned about gases, liquids, solids and intermolecular forces. In total, there are three main types of matter solids, liquids, and gases. In solids, the particles are in fixed positions. In liquids the particles can move, but only if they remain within the liquid. However, in gases the particles are able to spread out and move far away from each other. The state of matter is dependent on the temperature. However, different types of matter have differing melting, vaporization and boiling points.
When matter is in a solid state the bond which bind the molecules together are called ionic bonds. These are extremely strong bonds and they hold the matter together. Besides ionic bonds, if the molecules are polar they can have dipole forces which help to hold them together. If a hydrogen is covalently bonded to an electronegative atom, then often it is hydrogen bonds, which form between the slightly positively charge hydrogen and electronegative atoms such as nitrogen, oxygen or fluorine. An example of this is water. One final type of bond, which exists between nonpolar molecules is that of dispersion forces. Dispersion forces are also known as London dispersion forces.
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London dispersion forces are temporary forces which happen when the two molecules are aligned in such a way that it leads to the occurrence of a short-term dipole. The heavier the molecular weight of the molecule the strong the London dispersion force will be. Of all the types of forces that were described in this chapter, London dispersion forces, are the weakest force. The stronger version of this force, which happens when a large dipole is formed, are often called dipole-dipole forces. Together London dispersion forces and dipole-dipole forces are referred to as Van der Waals forces. Even though these two types of forces are weak they are still extremely important for the binding of matter in nonpolar molecules. While much is known about these types of forces, new research is still being published on the role that they play in different types of compounds. Recently in 2015, a study was published which investigated the role of London dispersion forces in glove and silver clusters on anatase (TiO2) and zirconium dioxide (ZrO2) surfaces (Puigdollers et al., 2015).
Understanding the forces which are exerted by these compounds on these surfaces is important because of the types of applications that these metal coated surfaces are used in. Recently there has been an interest in using these metal-surface combinations for nucleation and in the development of stable metal nanoparticles. In this article, the authors found that on these surfaces that while dispersion forces are often considered to be negligible they are extremely important in predicting the stability and adsorption energies of the metal clusters. For this reason, the authors state that they must be included in stability and adsorption energy calculation (Puigdollers et al., 2015).
With respect to what I learned in the course, I previously only thought of metals as compounds such as aluminum, copper and gold, which can rust and can be used as catalysts for reactions. However, this paper showed me that there are many more applications for these compounds. Overall, this article highlighted the fact that while forces may be weak, they can still play a major role in determining the characteristics of the compound. As such I now have a new appreciation for the types of forces and how the interaction of these forces can lead to changes in the properties of the compound.
- Puigdollers, A. R., Schlexer, P., & Pacchioni, G. (2015). Gold and silver clusters on TiO2 and ZrO2 (101) surfaces: role of dispersion forces. The Journal of Physical Chemistry C, 119(27), 15381-15389.
