<P> 22 Na is a positron - emitting isotope with a remarkably long half - life . It is used to create test - objects and point - sources for positron emission tomography . </P> <Table> <Tr> <Th> nuclide symbol </Th> <Th> Z (p) </Th> <Th> N (n) </Th> <Th> isotopic mass (u) </Th> <Th> half - life </Th> <Th> decay mode (s) </Th> <Th> daughter isotope (s) </Th> <Th> nuclear spin </Th> <Th> representative isotopic composition (mole fraction) </Th> <Th> range of natural variation (mole fraction) </Th> </Tr> <Tr> <Th_colspan="3"> excitation energy </Th> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 7 </Td> <Td> 7001180259700000000 ♠ 18.025 97 (5) </Td> <Td> 6979129999999999999 ♠ 1.3 (4) × 10 s </Td> <Td> p (> 99.9%) </Td> <Td> Ne </Td> <Td> (1 −) #</Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β (<. 1%) </Td> <Td> Ne </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 8 </Td> <Td> 7001190138770000000 ♠ 19.013 877 (13) </Td> <Td> <40 ns </Td> <Td> p </Td> <Td> Ne </Td> <Td> (5 / 2 +) #</Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 9 </Td> <Td> 7001200073510000000 ♠ 20.007 351 (7) </Td> <Td> 447.9 (23) ms </Td> <Td> β (75%) </Td> <Td> Ne </Td> <Td> 2 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, α (25%) </Td> <Td> O </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 10 </Td> <Td> 7001209976552000000 ♠ 20.997 6552 (8) </Td> <Td> 22.49 (4) s </Td> <Td> β </Td> <Td> Ne </Td> <Td> 3 / 2 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 11 </Td> <Td> 7001219944364000000 ♠ 21.994 4364 (4) </Td> <Td> 2.6027 (10) y </Td> <Td> β </Td> <Td> Ne </Td> <Td> 3 + </Td> <Td> Trace </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td_colspan="3"> 583.03 (9) keV </Td> <Td> 244 (6) ns </Td> <Td> </Td> <Td> </Td> <Td> 1 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 12 </Td> <Td> 7001229897692809000 ♠ 22.989 769 2809 (29) </Td> <Td_colspan="3"> Stable </Td> <Td> 3 / 2 + </Td> <Td> 7000100000000000000 ♠ 1.0000 </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 13 </Td> <Td> 7001239909627800000 ♠ 23.990 962 78 (8) </Td> <Td> 7004538524000000000 ♠ 14.9590 (12) h </Td> <Td> β </Td> <Td> Mg </Td> <Td> 4 + </Td> <Td> Trace </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td_colspan="3"> 472.207 (9) keV </Td> <Td> 20.20 (7) ms </Td> <Td> IT (99.95%) </Td> <Td> Na </Td> <Td> 1 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β (. 05%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 14 </Td> <Td> 7001249899540000000 ♠ 24.989 9540 (13) </Td> <Td> 59.1 (6) s </Td> <Td> β </Td> <Td> Mg </Td> <Td> 5 / 2 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 15 </Td> <Td> 7001259926330000000 ♠ 25.992 633 (6) </Td> <Td> 1.077 (5) s </Td> <Td> β </Td> <Td> Mg </Td> <Td> 3 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 16 </Td> <Td> 7001269940770000000 ♠ 26.994 077 (4) </Td> <Td> 301 (6) ms </Td> <Td> β (99.87%) </Td> <Td> Mg </Td> <Td> 5 / 2 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n (. 13%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 17 </Td> <Td> 7001279989380000000 ♠ 27.998 938 (14) </Td> <Td> 30.5 (4) ms </Td> <Td> β (99.421%) </Td> <Td> Mg </Td> <Td> 1 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n (. 579%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 18 </Td> <Td> 7001290028610000000 ♠ 29.002 861 (14) </Td> <Td> 44.9 (12) ms </Td> <Td> β (74.09%) </Td> <Td> Mg </Td> <Td> 3 / 2 (+ #) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n (25.91%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 19 </Td> <Td> 7001300089760000000 ♠ 30.008 976 (27) </Td> <Td> 48.4 (17) ms </Td> <Td> β (68.83%) </Td> <Td> Mg </Td> <Td> 2 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n (30.0%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, 2n (1.17%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, α </Td> <Td> Ne </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 20 </Td> <Td> 7001310135900000000 ♠ 31.013 59 (23) </Td> <Td> 17.0 (4) ms </Td> <Td> β (62.05%) </Td> <Td> Mg </Td> <Td> (3 / 2 +) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, 2n </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, 3n </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 21 </Td> <Td> 7001320204700000000 ♠ 32.020 47 (38) </Td> <Td> 12.9 (7) ms </Td> <Td> β </Td> <Td> Mg </Td> <Td> (3 −, 4 −) </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, 2n </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 22 </Td> <Td> 7001330267200000000 ♠ 33.026 72 (94) </Td> <Td> 8.2 (2) ms </Td> <Td> β, n (52.0%) </Td> <Td> Mg </Td> <Td> 3 / 2 + #</Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β (36.0%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, 2n (12.0%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 23 </Td> <Td> 7001340351700000000 ♠ 34.035 17 (96) #</Td> <Td> 5.5 (10) ms </Td> <Td> β, 2n (50.0%) </Td> <Td> Mg </Td> <Td> 1 + </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β (35.0%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> β, n (15.0%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 24 </Td> <Td> 7001350424900000000 ♠ 35.042 49 (102) #</Td> <Td> 1.5 (5) ms </Td> <Td> β (> 99.9%) </Td> <Td> Mg </Td> <Td> 3 / 2 + #</Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> β, n (<. 1%) </Td> <Td> Mg </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 25 </Td> <Td> 36.05148 (102) #</Td> <Td> <260 ns </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> Na </Td> <Td> 11 </Td> <Td> 26 </Td> <Td> 37.05934 (103) #</Td> <Td> 1 #ms (> 1.5 μs) </Td> <Td> </Td> <Td> </Td> <Td> 3 / 2 + #</Td> <Td> </Td> <Td> </Td> </Tr> </Table> <Tr> <Th> nuclide symbol </Th> <Th> Z (p) </Th> <Th> N (n) </Th> <Th> isotopic mass (u) </Th> <Th> half - life </Th> <Th> decay mode (s) </Th> <Th> daughter isotope (s) </Th> <Th> nuclear spin </Th> <Th> representative isotopic composition (mole fraction) </Th> <Th> range of natural variation (mole fraction) </Th> </Tr> <Tr> <Th_colspan="3"> excitation energy </Th> </Tr>

Why sodium 24 isotope is rarely found in its natural state