English Vocabulary Flash Cards - Chemical Formulas @ englishpdf.com and englishteststore.com File 100 F2Sr strontium fluoride F2Th thorium difluoride F2Ti titanium difluoride F2Tl2 dithallium difluoride F2W tungsten difluoride F2Xe xenon difluoride F2Y yttrium difluoride F2Zn zinc difluoride