FTP, name this alkaline earth metal with atomic number 56 and chemical symbol
This element's pure form, which is not found in nature, is used to remove trace gases from vacuum tubes.  Combined with sulfate it is used as a filter for rubber, plastics and resins and since it does not dissolve in water can be ingested to produce X-rays of digestive tract.  It is present in witherite and its salts give a characteristic green color in the flame test.  FTP, name this alkaline earth metal with atomic number 56 and chemical symbol Ba [B-A].
This element's pure form, which is not found in nature, is used to remove trace gases from vacuum tubes.  
Barium