396 



T = Vi period 



Table 506. 

 RADIOACTIVITY. 



time when body is V2 transformed. A = transformation constant 



9 = i/\ is average life 



of radioactive atoms. Parentheses indicate feeble radiation. V is the velocity of the c. or ^ rays relative to that of 

 light. To convert to cm/sec multiply by 3X 10'". ao is the range of a particles in air 76 cm pres. o°Ci at other tem- 

 peratures and pressures, at = {ao (273 + t)76o| 7273 p. For o-rays, V = o.o342a^. 



Radioactive 

 Element 



Symbol 



Atomic 



Weight No 



T 



y™ period 



average life 



A (sec.-i) 



Uranium Radium Group 



238 



234 

 234 

 234 

 230 

 226 



222 

 218 

 214 

 214 

 214 

 210 

 210 

 210 

 206 



214 

 210 

 210 



4.67 X io»y 

 24.6 d 

 1. 15 m 

 2 X io»y 

 6.9 X 10* y 

 1690 y 

 3.85 d 

 30 m 

 26.8 m 

 19 S m 

 10-' s 



i6s y 



so d 

 136 d 



6.7s X io»y 

 355 d 

 1. 6s m 

 3 X lo'y 

 lo* y 

 2440 y 

 5-5S d 

 4.32 m 



38.7 m 

 28.1 m 

 io-« s 



23.8 y 

 7.2 d 

 196 d 



4-7 X 10-" 

 3.26 X 10-' 



O.OIO 

 lO-K (?) 



3.2 X 10-" 

 1.30 X io-i> 

 2.08 X 10-" 

 3.85 X 10-3 

 4.30 X io-< 

 S.92 X io-« 

 106 (?) 

 1.33 X io-» 

 1.61 X 10-6 

 S.90 X 10-8 



(1.8 X 10-') 



8.3 X 10-3 



Actinium Group 



Uranium ? 

 Uranium Y 

 Protoactinium 

 Actinium 

 Radioactinium 

 Actinium X 

 Actinon 

 Actinium A 

 Actinium B 

 Actinium C 

 Actinium C" 

 Actinium n" 



UY 



Pa 



Ac 



RdAc 



AcX 



An 



AcA 



AcB 



AcC 



AcC" 



Acn" 



1. 04 d 



1.2 X io< y 



20 y 



19 S d 



11.4 d 



3-9 s 



2.0 X 10-' s 



36.1 m 



2. IS m 



4.71 m 



i.Sd 



1.7 X io<y 

 28.8 y 

 28.1 d 

 16.4 d 

 S-6s 



2.9 X 10-' s 

 52. 1 m 



3.10 m 

 6.83 m 



7-8 X 10-6 

 1.9 X io-'2 

 i.i X 10-' 

 4. II X 10-' 

 7.06 X IO-' 

 0.178 

 345- 



3.2 X lo-" 

 S.37 X 10-' 

 2.44 X IO-' 



Thorium Group 



Thorium 

 Mesothorium i 

 Mesothorium 2 

 Radiothorium 

 Thorium X 

 Thoron 

 Thorium A 

 Thorium B 

 Thorium C ^ 

 Thorium C 

 Thorium CI' 



Thorium C J 

 Thorium C" 

 Thorium fi" 



Potassium 

 Rubidium 



Th 



MsThi 



MsTh2 



RaTh 



ThX 



Tn 



ThA 



ThB 



The 



The 



Thn' 



ThC 



ThC" 



Thn" 



232 

 228 

 228 

 228 

 224 

 220 

 216 

 212 

 212 

 212 

 208 



212 

 208 

 208 



K 

 Rb 



39-1 

 8S.S 



1.31 X 10' 

 6.7 y 

 6.2 h 

 2.02 y 

 364 d 

 S4 s 

 0.14 s 

 10.6 h 

 6c m 



Notes. — (i) i g U emits 2.37 X ic' a-particles per sec. (3) also called Brevium; (7) also called Radium Emanation 

 and Niton; inert pas, dens, iii H; boils — 6s° C, condenses low pressure —150° C. (10) has double disintegration; I 

 9907% emits 3-rays and give RaC'; rest, a-rays and give RaC"; (12) radiolead; (14) Polonium; (15) lead; (17) also! 

 called radium Cj; (18) hypothetical; (21) also called ekatantalum; Uranium Z, isotopic with Pa accompanies Ur in mi-1 

 nute quantities; period 6-7 h; /3-radiation; (2s) also called act. emanation, inert gas, condenses between —120 andj 

 — 150° C; (29) also called act. D; (36) also called th. emanation, inert gas. 



Smithsonian tables. 



