Lego is awesome! Just about everyone has spent some time assembling the colourful little blocks. Only a few pieces and you can make a huge variety of shapes. Take a look at the three figures below. Each is made from the same set of blocks: four yellow 1×2’s, one green 4×4, and one red 1×1. But many more different arrangements could be made. Because Lego has such a variety of blocks and attachment points the number of possible conformations grows very quickly. Dozens of arrangements could be made from this set alone.



The science of chemistry has a parallel concept. Molecules that are made from the same set of atoms but have different arrangements are called structural isomers, or some times just isomers for short.  You could definitely consider the Lego shapes above to be isomers – same set of pieces, different arrangements.  You might even go so far as to call them Legomers.

Getting back to chemistry, an isomer is a molecule that shares a chemical formula with another molecule (or molecules) but has a different arrangement of its constituent atoms.  The video below, from Virtual High School’s grade 12 chemistry course, SCH4U, discusses the definition of isomers and provides several great examples.

This video is part of a series on the chemistry of isomers.   Stay tuned for more videos on stereoisomers, enantiomers, and the biological applications of chiral molecules!  If you’d like to know more about isomers reach-out in the discussion below.  We’re happy to answer questions.  You can also follow the VHS science department on twitter with the handle @VHSScience.