Branch

move one carbon. is it a new molecule?

plasticine carbons on matchsticks: move an end carbon and the model renames itself from its longest chain, until every isomer of C5, C6 and C7 is written in the notebook

Isomers have the same formula and different joins. Bending a chain changes nothing: the name comes from the longest chain of carbons, numbered from the end that gives the branches the lowest numbers. A branch can hide part of the longest chain, so look for it around corners. C5H12 has 3 isomers, C6H14 has 5 and C7H16 has 9.

Concepts: chemistry, graphs, symmetry, combinatorics.

An interactive you play with one thumb, on Wundr.