Atomic mass

Atomic mass was a property of elements.

An Entity altered the atomic mass of hydrogen within the Iarcho's star, killing the species. (PROSE: From Eternity)

Silver had an atomic mass of 107.870. (PROSE: Wolfsbane)

When Martin Stowe asked for Romana I's number, she did not understand which number and asked if he meant atomic mass. (PROSE: The Glarn Strategy)

The Void Ship had no measurable heat, radiation, and atomic mass. (TV: Army of Ghosts)