Atomic weight

You may be looking for atomic mass.

Atomic weight was a property of elements on the periodic table.

Iron had an atomic weight of 55.84 while gold had an atomic weight of 19.2. (TV: The Evil of the Daleks) An alternate account stated that gold-197, gold-198, and gold-194 were three of its isotopes. (PROSE: Midnight in the Café of the Black Madonna)

According to Zoe Heriot, the atomic weight of tellurium was 128. (TV: The Krotons)

When a segment of the Key to Time was disguised as the planet Calufrax, it had an artificially metricised structure consisting of a substance with a variable atomic weight. (TV: The Pirate Planet) When looking for the fourth segment, the Doctor and Romana knew they were looking for any substance with a variable atomic weight. (PROSE: The Shadow of Weng-Chiang)

The Fourth Doctor assumed the Dodecahedron had an atomic weight of 200 and a dozen Tigellans could not have carried it away. (TV: Meglos)

When Oliver Malf researched pentatholene gas, he sae details of its atomic weight, formula, structural diagram and effects on sentient, warm-blooded, oxygen-breathing organisms. (PROSE: A Device of Death)

Jenny Meredith thought baby Anwen Williams was heavier than she looked and wanted to know her mean atomic weight. (PROSE: First Born)

Interplanetary Mining Corporation's preliminary checks of Lucifer confirmed the existence of a previously unknown, stable, and high-atomic-weight element in the planet's core. (PROSE: Lucifer Rising)

The Spire was a 300 kilometre high artefact on Canopus IV was made out of futurite, an isohedrally clustered crystalline allotrope of an artificially stabilised high atomic weight element. (PROSE: Ghost Devices)