Artists like to use molecular models for making sculptures. This has already been covered on this blog, but I'd like to expand on the subject a little further in this post.
Molecules have certain stable configurations, which are governed by the distribution of their electrons. This is described by something called valence shell electron pair repulsion theory. It's somewhat complicated, but just imagine that electrons are magnets on a sphere that want to be as close to the centre as possible, while being as far apart from each other as possible. So while atoms are always in motion, this means that on average they are found in only a small number of configurations in molecules:
This kind of spatial configuration is correctly rendered in the large sculpture 'Gas Molecule' commissioned from Marc Ruygrok by the NAM:
This sculpture is supposed to depict methane, or CH4, with a central carbon atom connected to four hydrogen atoms. Ruygrok has largely copied the common 'ball-and-stick' molecular model, only taking some liberty with the colour scheme.
Although molecules don't have a 'real' colour, there is a
convention, called Corey-Pauling-Koltun colouring, for using certain colours for certain atoms. The central atom in Ruygrok's model is carbon, which in this convention is always
associated with black, while blue is always associated with nitrogen. If
the shiny purple-ish hue of the central atom is considered significant, then
this is traditionally linked to phosphorous, but is today more commonly
associated with potassium.
These colours are nothing but
conventions, so it's not that Ruygrok's choice is wrong per se, but it also isn't 'right' to use blue in this case. Without any other information, any chemist will think this model represents ammonium, not the intended methane.
As already stated, this example uses the so-called ball and stick model, but a more realistic space filling model exists where atoms are depicted as overlapping spheres representing their Van der Waals surface. Molecules in this model consist of interconnected spheres, so that a good separation through size and colour becomes even more important than it is in the ball and stick model. With this in mind, let me present to you 'Calcium 4-[4-(2-methylaninlino)-2,4-dioxobutyl]diazenyl-3-nitrobenzenesulfonate (C.I.13940)' by Jean-Luc Moulène:
This is supposedly a model of the molecular structure of a pigment, Yellow 62, which is then painted in the colour of this pigment. I already pointed out that without adequate differentiation through colour, such a model is hardly able to serve its clarifying function.
It is however clear that Moulène didn't correctly render the molecule he meant to render. When I looked up and drew a model of the pigment, I came up with the following structure:
Even without knowing anything about chemistry, it's obvious that these are are two different structures. In the correct model, there are 41 spheres present, while in Moulène's sculpture one only counts 29 spheres. I did notice that in Moulène's sculpture no hydrogen atoms were depicted, which is somewhat common practice. I therefore counted the amount of hydrogen atoms that should be present, of which there are 15, so if the difference came from the absence of hydrogen, then the amount of spheres would be 26. I therefore have no explanation of where the artist went astray in rendering his model, but it is clear that the molecular model doesn't depict the pigment that he claims.
This could also already be gleaned from the inclusion of 'Calcium' in the sculpture's title. Organocalcium compounds are very uncommon and so the inclusion of calcium in the name most likely means that this is a salt. The SO31- sulphonate group in the molecule, shown in yellow with red, is very reactive and needs to be ionically bonded to a positively charged atom, Ca2+ in this case, to be stable. The double positive charge on the calcium ion is paired with two single negative charges on the other compound, which means that there must be two of the previously shown molecule in the following configuration:
This is of course looks nothing like the molecule in Moulène's sculpture and anybody with knowledge of chemistry could have spotted the error merely from the first word of the title.
I then noticed the following drawing on the cover of Keith Tyson's publication 'Molecular Compound No 4.':
Comparing this image with the VSEPR models at the beginning of this post, it should be clear that this drawing is not based on any existing molecule. Upon consulting the book, it turned out to contain no further references to reality and consist only of the fantastical imaginings of the artist, so I won't make any further comment on this publication.
I could list more examples of artists that have attempted to employ molecular models, but in short all of these sculptures I've encountered forgone scientific accuracy in some way.
The only one I know of that isn't necessarily wrong was a sculpture that simply used nothing but a commercially available molecular modelling kit. So while this was possibly accurate, it's artistic value was also negligible.
And the reason I've written all this is because I researched the subject while making the following model of a molecule called methyl mercaptan:
Methyl mercaptan, or CH3SH, is one of the molecules that make farts smell. This model is made of a tennis ball, a black golf ball and four small roulette balls. These generic, store bought, balls are both the right colour and approximately the right size for a CPK-model for a molecular structure, as can be seen in this rendering taken from a molecular drawing program:
This is thus an indication that it's possible to have a novel approach to creating a molecular model without necessarily having to significantly compromise its scientific accuracy.
