You time travel 100 years into the future and learn that

Last updated: 7/26/2022

You time travel 100 years into the future and learn that several new elements have been discovered, as pictured. These elements are frequently found as oxides, and need to be separated in order to extract the pure element. Before going through this effort, it is useful to know what amount of the element can be extracted. What is the mass percent composition of element A in the compound A505?