Atomic number
Atomic number was a property of elements on the periodic table. (TV: Shada)
According to the Eighth Doctor, the atomic number of beryllium was 4. (PROSE: The Deadstone Memorial)
According to the Thirteenth Doctor, the atomic number of antimony was 51. (TV: The Tsuranga Conundrum)
According to Zoe Heriot, the atomic number of tellurium was 52. (TV: The Krotons, PROSE: The Krotons)
According to the Twelfth Doctor, the atomic number of caesium was 55. (TV: Flatline)
According to Señor 105, the atomic number of neptunium was 93. (PROSE: Elementary, My Dear Sheila)
According to Iris Wildthyme, the atomic number of dubnium was 105. In 1968, this element was known as hahnium. (PROSE: Iris Wildthyme y Señor Cientocinco contra Los Monstruos del Fiesta)