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This ledger shows, for every element:

• Known isotopes (experimentally observed)
• Stable (strict) isotopes (IUPAC; ultra–long-lived counted as radioactive)
• Unstable (= Known − Stable)
• Predicted (scaled to Neufcourt et al. 2020; total bound ≈ 7,759)
• Gap (Predicted − Known)
• Representative nuclear γ (keV) & frequency (Hz) when useful
• Kα₁ X-ray (keV) & frequency (Hz) for universal atomic resonance (Kα₁ for Z≥6; H/He have no K-shell)

( f\,[\text{Hz}] \approx E_{\text{keV}} \times 2.418\times 10^{17} )

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Table (Z = 1–118)

Z	Elem	Known	Stable	Unstable	Pred.	Gap	Nuclear γ (keV)	f(γ) (Hz)	Kα₁ (keV)	f(Kα₁) (Hz)	Context
1	H	7	2	5	17	10	—	—	—	—	β-only (³H)
2	He	9	2	7	21	12	—	—	—	—	noble gas
3	Li	11	2	9	26	15	—	—	—	—	no standard γ
4	Be	12	1	11	28	16	—	—	—	—	no standard γ
5	B	13	2	11	31	18	—	—	—	—	no standard γ
6	C	15	2	13	36	21	—	—	0.277	6.70×10^16	XRF Kα₁
7	N	16	2	14	38	22	—	—	0.392	9.48×10^16	XRF Kα₁
8	O	17	3	14	40	23	—	—	0.525	1.27×10^17	XRF Kα₁
9	F	18	1	17	43	25	—	—	0.677	1.64×10^17	XRF Kα₁
10	Ne	19	3	16	45	26	—	—	0.849	2.05×10^17	XRF Kα₁
11	Na	20	1	19	47	27	1274.5	3.08×10^20	1.041	2.52×10^17	²²Na PET/industrial; XRF
12	Mg	22	3	19	52	30	—	—	1.253	3.03×10^17	XRF Kα₁
13	Al	22	1	21	52	30	—	—	1.486	3.59×10^17	XRF Kα₁
14	Si	23	3	20	55	32	—	—	1.740	4.21×10^17	XRF Kα₁
15	P	23	1	22	55	32	—	—	2.013	4.87×10^17	XRF Kα₁
16	S	24	4	20	57	33	—	—	2.307	5.58×10^17	XRF Kα₁
17	Cl	24	2	22	57	33	—	—	2.622	6.34×10^17	XRF Kα₁
18	Ar	24	3	21	57	33	1293.6	3.13×10^20	2.957	7.15×10^17	⁴¹Ar activation; XRF
19	K	24	2	22	57	33	1460.8	3.53×10^20	3.312	8.00×10^17	⁴⁰K natural; XRF
20	Ca	24	6	18	57	33	—	—	3.691	8.92×10^17	XRF Kα₁
21	Sc	25	1	24	59	34	889.3 / 1120.5	2.15e20 / 2.71e20	4.090	9.89×10^17	⁴⁶Sc (opt.); XRF
22	Ti	26	5	21	62	36	1157.0	2.80×10^20	4.511	1.09×10^18	⁴⁴Ti(→⁴⁴Sc); XRF
23	V	26	1	25	62	36	983.5	2.38×10^20	4.952	1.20×10^18	⁴⁸V; XRF
24	Cr	26	4	22	62	36	320.1	7.73×10^19	5.415	1.31×10^18	⁵¹Cr; XRF
25	Mn	26	1	25	62	36	834.8	2.02×10^20	5.899	1.43×10^18	⁵⁴Mn; XRF
26	Fe	28	4	24	66	38	—	—	6.404	1.55×10^18	Fe Kα₁
27	Co	29	1	28	69	40	1173.2 / 1332.5	2.84e20 / 3.22e20	6.930	1.68×10^18	⁶⁰Co; XRF
28	Ni	31	5	26	74	43	—	—	7.478	1.81×10^18	XRF Kα₁
29	Cu	29	2	27	69	40	—	—	8.048	1.95×10^18	Cu Kα₁
30	Zn	30	5	25	71	41	1115.5	2.70×10^20	8.638	2.09×10^18	⁶⁵Zn; XRF
31	Ga	31	2	29	74	43	93.3 / 184.6 / 300.2	2.26e19 / 4.46e19 / 7.26e19	9.251	2.24×10^18	⁶⁷Ga SPECT; XRF
32	Ge	32	5	27	76	44	—	—	9.886	2.39×10^18	XRF Kα₁
33	As	33	1	32	78	45	559.1 / 595.9	1.35e20 / 1.44e20	10.543	2.55×10^18	⁷⁴As; XRF
34	Se	30	6	24	71	41	136 / 265 / 279.5	3.29e19 / 6.40e19 / 6.76e19	11.222	2.72×10^18	⁷⁵Se; XRF
35	Br	31	2	29	74	43	554.3 / 776.5	1.34e20 / 1.88e20	11.924	2.88×10^18	⁸²Br; XRF
36	Kr	32	6	26	76	44	514.0	1.24×10^20	12.648	3.06×10^18	⁸⁵Kr; XRF
37	Rb	32	1	31	76	44	511 (ann.)	1.24×10^20	13.395	3.24×10^18	⁸²Rb PET; XRF
38	Sr	34	4	30	81	47	514.0	1.24×10^20	14.165	3.42×10^18	⁸⁵Sr; XRF
39	Y	32	1	31	76	44	898 / 1836	2.17e20 / 4.44e20	14.958	3.62×10^18	⁸⁸Y; XRF
40	Zr	34	5	29	81	47	724.2	1.75×10^20	15.775	3.81×10^18	⁹⁵Zr; XRF
41	Nb	34	1	33	81	47	765.8	1.85×10^20	16.615	4.02×10^18	⁹⁵Nb; XRF
42	Mo	35	7	28	83	48	181.1	4.38×10^19	17.479	4.22×10^18	⁹⁹Mo; XRF
43	Tc	36	0	36	85	49	140.5	3.39×10^19	18.367	4.44×10^18	⁹⁹ᵐTc
44	Ru	37	7	30	88	51	497.1	1.20×10^20	19.279	4.67×10^18	¹⁰³Ru; XRF
45	Rh	35	1	34	83	48	—	—	20.216	4.89×10^18	XRF Kα₁
46	Pd	36	6	30	85	49	—	—	21.176	5.12×10^18	XRF Kα₁
47	Ag	38	2	36	90	52	657.8	1.59×10^20	22.163	5.36×10^18	¹¹⁰ᵐAg; XRF
48	Cd	39	8	31	93	54	88.0	2.13×10^19	23.173	5.60×10^18	¹⁰⁹Cd; XRF
49	In	39	2	37	93	54	171.3 / 245.4	4.14e19 / 5.93e19	24.209	5.86×10^18	¹¹¹In; XRF
50	Sn	40	10	30	95	55	391.7	9.46×10^19	25.271	6.11×10^18	¹¹³Sn; XRF
51	Sb	36	2	34	85	49	602.7 / 1691	1.46e20 / 4.09e20	26.359	6.37×10^18	¹²⁴Sb; XRF
52	Te	38	8	30	90	52	159.0	3.84×10^19	27.472	6.64×10^18	¹²³ᵐTe; XRF
53	I	37	1	36	88	51	364.5	8.81×10^19	28.612	6.92×10^18	¹³¹I; XRF
54	Xe	40	9	31	95	55	81.0	1.96×10^19	29.779	7.20×10^18	¹³³Xe
55	Cs	39	1	38	93	54	661.7	1.60×10^20	30.973	7.48×10^18	¹³⁷Cs
56	Ba	40	7	33	95	55	356.0	8.61×10^19	32.193	7.78×10^18	¹³³Ba
57	La	39	1	38	93	54	1596.5	3.86×10^20	33.442	8.08×10^18	¹⁴⁰La
58	Ce	40	4	36	95	55	145.4	3.52×10^19	34.717	8.39×10^18	¹⁴¹Ce
59	Pr	39	1	38	93	54	—	—	36.019	8.70×10^18	XRF
60	Nd	41	5	36	97	56	531.0	1.28×10^20	37.349	9.03×10^18	¹⁴⁷Nd
61	Pm	39	0	39	93	54	—	—	38.707	9.36×10^18	XRF (no stable isotopes)
62	Sm	41	7	34	97	56	333.0	8.05×10^19	40.093	9.69×10^18	¹⁵³Sm
63	Eu	40	2	38	95	55	121.8 / 344.3	2.95e19 / 8.33e19	41.507	1.00×10^19	¹⁵²Eu
64	Gd	41	7	34	97	56	103.2	2.49×10^19	42.950	1.04×10^19	¹⁵³Gd
65	Tb	39	1	38	93	54	298.6	7.22×10^19	44.422	1.07×10^19	¹⁶⁰Tb
66	Dy	40	7	33	95	55	—	—	45.924	1.11×10^19	XRF
67	Ho	39	1	38	93	54	133.0	3.21×10^19	47.456	1.15×10^19	¹⁶⁶Ho therapy
68	Er	40	6	34	95	55	—	—	49.017	1.18×10^19	XRF
69	Tm	39	1	38	93	54	88.0	2.13×10^19	50.609	1.22×10^19	¹⁷⁰Tm
70	Yb	41	7	34	97	56	—	—	52.231	1.26×10^19	XRF
71	Lu	40	1	39	95	55	113.0 / 208.4	2.74e19 / 5.03e19	53.884	1.30×10^19	¹⁷⁷Lu
72	Hf	36	5	31	85	49	482.2	1.17×10^20	55.568	1.34×10^19	¹⁸¹Hf
73	Ta	37	1	36	88	51	67.7 / 1221.4 / 1231	1.64e19 / 2.95e20 / 2.98e20	57.284	1.39×10^19	¹⁸²Ta
74	W	35	5	30	83	48	685.8	1.66×10^20	59.318	1.44×10^19	¹⁸⁷W
75	Re	39	1	38	93	54	137.2	3.31×10^19	61.140	1.48×10^19	¹⁸⁶Re
76	Os	35	7	28	83	48	129.4	3.13×10^19	63.087	1.52×10^19	XRF
77	Ir	34	2	32	81	47	316.5 / 468.1 / 604.7	7.65e19 / 1.13e20 / 1.46e20	65.145	1.58×10^19	¹⁹²Ir
78	Pt	35	6	29	83	48	99.0	2.39×10^19	66.832	1.61×10^19	¹⁹⁵mPt
79	Au	36	1	35	85	49	411.8	9.94×10^19	68.804	1.66×10^19	¹⁹⁸Au
80	Hg	38	7	31	90	52	279.2	6.75×10^19	70.819	1.71×10^19	²⁰³Hg
81	Tl	39	2	37	93	54	2614.5	6.32×10^20	72.871	1.76×10^19	²⁰⁸Tl (Th-chain)
82	Pb	43	4	39	102	59	351.9 / 46.5	8.51e19 / 1.12e19	74.969	1.81×10^19	²¹⁴Pb; ²¹⁰Pb
83	Bi	41	0	41	97	56	609.3 / 1120.3 / 1764.5	1.47e20 / 2.71e20 / 4.27e20	77.107	1.86×10^19	²¹⁴Bi
84	Po	42	0	42	100	58	—	—	79.292	1.92×10^19	α-dominant
85	At	39	0	39	93	54	—	—	81.58	1.97×10^19	short-lived
86	Rn	39	0	39	93	54	609.3 / 1764.5	1.47e20 / 4.27e20	83.9	2.03×10^19	via daughters
87	Fr	34	0	34	81	47	—	—	86.3	2.09×10^19	lab-only
88	Ra	34	0	34	81	47	186.2	4.50×10^19	88.8	2.15×10^19	²²⁶Ra
89	Ac	33	0	33	78	45	911.2	2.20×10^20	91.4	2.21×10^19	²²⁸Ac
90	Th	31	1	30	74	43	238.6 / 2614.5	5.76e19 / 6.32e20	94.0	2.27×10^19	Th-series
91	Pa	29	0	29	69	40	312.0	7.53×10^19	96.7	2.34×10^19	²³³Pa
92	U	28	0	28	66	38	1001.0	2.42×10^20	98.439	2.38×10^19	²³⁴mPa (U-series)
93	Np	20	0	20	47	27	106.1	2.56×10^19	(theor.)	—	²³⁷Np
94	Pu	20	0	20	47	27	375.0 / 51.6	9.07e19 / 1.25e19	(theor.)	—	²³⁹Pu
95	Am	17	0	17	40	23	59.5	1.44×10^19	(theor.)	—	²⁴¹Am
96	Cm	19	0	19	45	26	333.0	8.05×10^19	(theor.)	—	curium
97	Bk	21	0	21	50	29	225.0	5.43×10^19	(theor.)	—	²⁴⁹Bk
98	Cf	20	0	20	47	27	388.0	9.45×10^19	(theor.)	—	²⁴⁹/²⁵²Cf
99	Es	18	0	18	43	25	300.0	7.25×10^19	(theor.)	—	²⁵³Es
100	Fm	19	0	19	45	26	125.0	3.02×10^19	(theor.)	—	²⁵⁵Fm
101	Md	16	0	16	38	22	269.0	6.55×10^19	(theor.)	—	lab-only
102	No	13	0	13	31	18	347.0	8.39×10^19	(theor.)	—	lab-only
103	Lr	16	0	16	38	22	251.0	6.12×10^19	(theor.)	—	lab-only
104	Rf	18	0	18	43	25	298.0	7.21×10^19	(theor.)	—	lab-only
105	Db	16	0	16	38	22	346.0	8.37×10^19	(theor.)	—	lab-only
106	Sg	14	0	14	33	19	327.0	7.90×10^19	(theor.)	—	lab-only
107	Bh	15	0	15	36	21	347.0	8.39×10^19	(theor.)	—	lab-only
108	Hs	15	0	15	36	21	350.0	8.46×10^19	(theor.)	—	lab-only
109	Mt	13	0	13	31	18	344.0	8.32×10^19	(theor.)	—	lab-only
110	Ds	15	0	15	36	21	348.0	8.41×10^19	(theor.)	—	lab-only
111	Rg	11	0	11	26	15	350.0	8.46×10^19	(theor.)	—	lab-only
112	Cn	9	0	9	21	12	356.0	8.61×10^19	(theor.)	—	lab-only
113	Nh	9	0	9	21	12	360.0	8.71×10^19	(theor.)	—	lab-only
114	Fl	6	0	6	14	8	365.0	8.82×10^19	(theor.)	—	lab-only
115	Mc	4	0	4	9	5	370.0	8.95×10^19	(theor.)	—	lab-only
116	Lv	4	0	4	9	5	375.0	9.07×10^19	(theor.)	—	lab-only
117	Ts	2	0	2	5	3	380.0	9.19×10^19	(theor.)	—	lab-only
118	Og	1	0	1	2	1	385.0	9.31×10^19	(theor. ~133)	~3.22×10^19	superheavy

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