Half-life of radium is:

Ans: C (1626 years) [Ref: Grainger & Allison Radiology 6th/118; Harrison 17th/1360; Dutta Gynaecology 5th/484, 4th/465 ; Merdith Radiation Physics & Nuclear Medicine/28)T1/2 of Ra-226 : 1626 years ~(1602yr- Harrison 17th/1369; 1620- Dutta Gynaecology 5th/484; 1622- Merdith Radiation physics & nuclear medicine/28). On various internet sites T1/2 of Ra-226 range from 1599-1626Table 223-1(Harrison): Internal Contaminant Radionuclides: Properties and TreatmentIsotope NameSymbolRadiation Type t 1/2 Radiologic t 1/2 Biologic, daysCobaltCo-60b, g 5.26 y 9.5RadiumRa-226a, b, g 1602 g 16,400Table : Merdith Radiation phvsics & nuclear medicine/28RaysRadioactive elementst 1/2 bP-32Sr-90Y-90PhosphorousStrontiumYttrium14.3 days28 years2.54 daysb, gRa-226Au-198I -131RadiumGoldIodine (mainly b)1622 years2.7 days8 daysgIr-192Co-60Cs-137Xe-133I-123I-132Tc-99Ga-70Tl-201Rn-222Cr-51K-81SeIridiumCobaltCesiumXenonIodineIodineTechnitiumGallium citrateThallous chlorideRadonChromiumKryptonSelenium74.5 days5.2years30 years5.2 days13 hours2.3 hours6 hours3.2 days3.1 days3-6 daysN, gCf- 252Ta-182CaliforniumTantalum2.6 years4 months