Original: 15 5 | - style = '' background-color : #c 0ffff '' | Argon | | Ar | | 18 | | 39.948 ( 1 ) The isotopic composition varies in terrestrial material such that a more precise atomic weight can not be given .
Simplified: 15 5 | - | Argon | | Ar | | 18 | | 39.948 ( 1 ) The isotopic composition varies in terrestrial material such that a more precise atomic weight can not be given .