Isotopes of magnesium
List of isotopes
Bold for stable isotopes Used in radiodating events early in the Solar System's history

Isotopes of magnesium

Section Title: List of isotopes
Table Section Text: Bold for stable isotopes Used in radiodating events early in the Solar System's history

nuclide symbol	Z(p)	N(n)	isotopic mass (u)	half-life	decay mode(s)	daughter isotope(s)	nuclear spin and parity	representative isotopic composition (mole fraction)	range of natural variation (mole fraction)

19Mg	12	7	19.03417(5)	5(3) ps	2p	17Ne	1/2−#

20Mg	12	8	20.0187631(2)	93(5) ms	β+ (69.7%)	20Na	0+

β+, p (30.3%)	19Ne

21Mg	12	9	21.0117058(8)	118.6(5) ms	β+ (66.9%)	21Na	5/2+

β+, p (32.6%)	20Ne

β+, α (0.5%)	17F

22Mg	12	10	21.9995707(3)	3.8755(12) s	β+	22Na	0+

23Mg	12	11	22.99412394(17)	11.317(11) s	β+	23Na	3/2+

24Mg	12	12	23.985041697(14)	Stable	0+	0.7899(4)	0.78958–0.79017

25Mg	12	13	24.98583696(5)	Stable	5/2+	0.1000(1)	0.09996–0.10012

26Mg	12	14	25.98259297(3)	Stable	0+	0.1101(3)	0.10987–0.11030

27Mg	12	15	26.98434063(5)	9.435(27) min	β−	27Al	1/2+

28Mg	12	16	27.9838766(21)	20.915(9) h	β−	28Al	0+

29Mg	12	17	28.988617(12)	1.30(12) s	β−	29Al	3/2+

30Mg	12	18	29.990463(4)	313(4) ms	β− (99.94%)	30Al	0+

β−, n (0.06%)	29Al

31Mg	12	19	30.996648(3)	236(20) ms	β− (93.8%)	31Al	1/2(+)

β−, n (6.2%)	30Al

32Mg	12	20	31.999110(4)	86(5) ms	β− (94.5%)	32Al	0+

β−, n (5.5%)	31Al

33Mg	12	21	33.005327(3)	90.5(16) ms	β− (86%)	33Al	3/2−

β−, n (14%)	32Al

34Mg	12	22	34.00894(3)	20(10) ms	β− (70%)	34Al	0+

β−, n (30%)	33Al

35Mg	12	23	35.01679(29)	70(40) ms	β−, n (52%)	34Al	7/2−#

β− (48%)	35Al

36Mg	12	24	36.02188(74)	3.9(13) ms	β−	36Al	0+

37Mg	12	25	37.03029(75)	8(4) ms	β−	37Al	(3/2−)

β−, n	36Al

38Mg	12	26	38.03658(54)#	1# ms [>260 ns]	0+

40Mg	12	28	40.05191(54)#	1# ms	β−, n	39Al	0+

β−	40Al

Sentence(s)

The longest-lived isotope is ²⁸Mg, with a half-life of 20.915 hours.

final_sentence: The longest-lived isotope is ²⁸Mg, with a half-life of 20.915 hours.