Condominium. Found mostly in urban areas, this element is thought to be a product of the well-known atomic decay that sets in during gentrification of a previously working-class neighborhood.

Dijonium. Unstable unless suspended in vinegar, Dijonium is now known to be present in significant amounts only in the soil of the Côte-d’Or department in France. It is the reason why no so-called “Dijon” mustard from anywhere else in the world tastes anything like the real thing.

Geranium. A perennial element with 10 stamens and one- to three-flowered peduncles on forking stems. Not to be confused with Pelargonium.

Gymnasium. This element was first isolated in an old pair of socks left in a locker at the YMCA in McKeesport, Penna. It has been kept isolated since then, for what scientists describe as obvious reasons.

Herbarium. First detected in dried botanical specimens, this radioactive element can affect the brain and is known to cause unseemly wrangling over seemingly straightforward generic divisions.

Triclinium. A very exclusive element found only in the ancient house of Trimalchio in Rome, whither it was brought at ruinous expense from God knows where.

Trivium. Not much use to anyone, this element nevertheless seems to commandeer the bulk of the conversation at chemists’ cocktail parties.