actinon

[ak-tuh-non] /ˈæk təˌnɒn/
noun, Chemistry
1.
a chemically inert, gaseous, short-lived isotope of radon that is a member of the actinium series. Symbol: An; atomic number: 86; atomic weight: 219.
Also called actinium emanation.
Origin
1925-30; < Neo-Latin; see actinium, -on2
British Dictionary definitions for actinon

actinon

/ˈæktɪˌnɒn/
noun
1.
a radioisotope of radon that is a decay product of radium. Symbol: An or 219Rn; atomic no: 86; half-life: 3.92s
2.
another name for actinide
Word Origin
C20: New Latin, from actinium + -on