The electronic and molecular structure of the acylium cation ([CH[subscript 3]CO][superscript +], 1) receives varied treatment in undergraduate textbooks and online resources. The overall structure of 1 is typically represented as an equal combination of resonance structures containing C-O triple and double bonds, the latter structure occasionally being shown with a bent C-C-O bond angle. This description is inconsistent with available experimental and theoretical data, all of which indicate that 1 is a linear molecule containing a C[triple bar]O bond, and can lead students to a false conception of structure, conjugation, and charge distribution. A set of simple computational exercises is reported that allows students to calculate and rationalize the most accurate resonance representation of 1.