Isotopes of radium

Radium (88Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given. The longest lived, and most common, isotope of radium is 226Ra with a half-life of 1,600 years. 226Ra occurs in the decay chain of 238U (often referred to as the radium series.) Radium has 33 known isotopes from 202Ra to 234Ra.

In 2013 it was discovered that the nucleus of radium-224 is pear-shaped.[1] This was the first discovery of an asymmetric nucleus.

Main isotopes of radium (88Ra)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
223Ra trace 11.43 d α 219Rn
224Ra trace 3.6319 d α 220Rn
225Ra trace 14.9 d β 225Ac
226Ra trace 1600 y α 222Rn
228Ra trace 5.75 y β 228Ac

Actinides vs fission products

Actinides and fission products by half-life
Actinides[2] by decay chain Half-life
range (y)
Fission products of 235U by yield[3]
4n 4n+1 4n+2 4n+3
4.5–7% 0.04–1.25% <0.001%
228Ra 4–6 155Euþ
244Cmƒ 241Puƒ 250Cf 227Ac 10–29 90Sr 85Kr 113mCdþ
232Uƒ 238Puƒ 243Cmƒ 29–97 137Cs 151Smþ 121mSn
248Bk[4] 249Cfƒ 242mAmƒ 141–351

No fission products
have a half-life
in the range of
100–210 k years ...

241Amƒ 251Cfƒ[5] 430–900
226Ra 247Bk 1.3 k – 1.6 k
240Pu 229Th 246Cmƒ 243Amƒ 4.7 k – 7.4 k
245Cmƒ 250Cm 8.3 k – 8.5 k
239Puƒ 24.1 k
230Th 231Pa 32 k – 76 k
236Npƒ 233Uƒ 234U 150 k – 250 k 99Tc 126Sn
248Cm 242Pu 327 k – 375 k 79Se
1.53 M 93Zr
237Npƒ 2.1 M – 6.5 M 135Cs 107Pd
236U 247Cmƒ 15 M – 24 M 129I
244Pu 80 M

... nor beyond 15.7 M years[6]

232Th 238U 235Uƒ№ 0.7 G – 14.1 G

Legend for superscript symbols
₡  has thermal neutron capture cross section in the range of 8–50 barns
ƒ  fissile
metastable isomer
№  primarily a naturally occurring radioactive material (NORM)
þ  neutron poison (thermal neutron capture cross section greater than 3k barns)
†  range 4–97 y: Medium-lived fission product
‡  over 200,000 y: Long-lived fission product

List of isotopes

Z(p) N(n)  
isotopic mass (u)
half-life decay
mode(s)[7][n 1]
isotope(s)[n 2]
spin and
(mole fraction)
range of natural
(mole fraction)
excitation energy
202Ra 88 114 202.00989(7) 2.6(21) ms
[0.7(+33−3) ms]
203Ra 88 115 203.00927(9) 4(3) ms α 199Rn (3/2−)
β+ (rare) 203Fr
203mRa 220(90) keV 41(17) ms α 199Rn (13/2+)
β+ (rare) 203Fr
204Ra 88 116 204.006500(17) 60(11) ms
[59(+12−9) ms]
α (99.7%) 200Rn 0+
β+ (.3%) 204Fr
205Ra 88 117 205.00627(9) 220(40) ms
[210(+60−40) ms]
α 201Rn (3/2−)
β+ (rare) 205Fr
205mRa 310(110)# keV 180(50) ms
[170(+60−40) ms]
α 201Rn (13/2+)
IT (rare) 205Ra
206Ra 88 118 206.003827(19) 0.24(2) s α 202Rn 0+
207Ra 88 119 207.00380(6) 1.3(2) s α (90%) 203Rn (5/2−,3/2−)
β+ (10%) 207Fr
207mRa 560(50) keV 57(8) ms IT (85%) 207Ra (13/2+)
α (15%) 203Rn
β+ (.55%) 207Fr
208Ra 88 120 208.001840(17) 1.3(2) s α (95%) 204Rn 0+
β+ (5%) 208Fr
208mRa 1800(200) keV 270 ns (8+)
209Ra 88 121 209.00199(5) 4.6(2) s α (90%) 205Rn 5/2−
β+ (10%) 209Fr
210Ra 88 122 210.000495(16) 3.7(2) s α (96%) 206Rn 0+
β+ (4%) 210Fr
210mRa 1800(200) keV 2.24 µs (8+)
211Ra 88 123 211.000898(28) 13(2) s α (97%) 207Rn 5/2(−)
β+ (3%) 211Fr
212Ra 88 124 211.999794(12) 13.0(2) s α (85%) 208Rn 0+
β+ (15%) 212Fr
212m1Ra 1958.4(5) keV 10.9(4) µs (8)+
212m2Ra 2613.4(5) keV 0.85(13) µs (11)−
213Ra 88 125 213.000384(22) 2.74(6) min α (80%) 209Rn 1/2−
β+ (20%) 213Fr
213mRa 1769(6) keV 2.1(1) ms IT (99%) 213Ra 17/2−#
α (1%) 209Rn
214Ra 88 126 214.000108(10) 2.46(3) s α (99.94%) 210Rn 0+
β+ (.06%) 214Fr
215Ra 88 127 215.002720(8) 1.55(7) ms α 211Rn (9/2+)#
215m1Ra 1877.8(5) keV 7.1(2) µs (25/2+)
215m2Ra 2246.9(5) keV 1.39(7) µs (29/2−)
215m3Ra 3756.6(6)+X keV 0.555(10) µs (43/2−)
216Ra 88 128 216.003533(9) 182(10) ns α 212Rn 0+
EC (1×10−8%) 216Fr
217Ra 88 129 217.006320(9) 1.63(17) µs α 213Rn (9/2+)
218Ra 88 130 218.007140(12) 25.2(3) µs α 214Rn 0+
β+β+ (rare) 218Rn
219Ra 88 131 219.010085(9) 10(3) ms α 215Rn (7/2)+
220Ra 88 132 220.011028(10) 17.9(14) ms α 216Rn 0+
221Ra 88 133 221.013917(5) 28(2) s α 217Rn 5/2+
CD (1.2×10−10%) 207Pb
222Ra 88 134 222.015375(5) 38.0(5) s α 218Rn 0+
CD (3×10−8%) 208Pb
223Ra[n 3] Actinium X 88 135 223.0185022(27) 11.43(5) d α 219Rn 3/2+ Trace[n 4]
CD (6.4×10−8%) 209Pb
224Ra Thorium X 88 136 224.0202118(24) 3.6319(23) d α 220Rn 0+ Trace[n 5]
CD (4.3×10−9%) 210Pb
225Ra 88 137 225.023612(3) 14.9(2) d β 225Ac 1/2+
226Ra Radium[n 6] 88 138 226.0254098(25) 1600(7) y α 222Rn 0+ Trace[n 7]
ββ (rare) 226Th
CD (2.6×10−9%) 212Pb
227Ra 88 139 227.0291778(25) 42.2(5) min β 227Ac 3/2+
228Ra Mesothorium 1 88 140 228.0310703(26) 5.75(3) y β 228Ac 0+ Trace[n 5]
229Ra 88 141 229.034958(20) 4.0(2) min β 229Ac 5/2(+)
230Ra 88 142 230.037056(13) 93(2) min β 230Ac 0+
231Ra 88 143 231.04122(32)# 103(3) s β 231Ac (5/2+)
231mRa 66.21(9) keV ~53 µs (1/2+)
232Ra 88 144 232.04364(30)# 250(50) s β 232Ac 0+
233Ra 88 145 233.04806(50)# 30(5) s β 233Ac 1/2+#
234Ra 88 146 234.05070(53)# 30(10) s β 234Ac 0+
  1. ^ Abbreviations:
    CD: Cluster decay
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes
  3. ^ Used for treating bone cancer
  4. ^ Intermediate decay product of 235U
  5. ^ a b Intermediate decay product of 232Th
  6. ^ Source of element's name
  7. ^ Intermediate decay product of 238U


  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.


  1. ^ "First observations of short-lived pear-shaped atomic nuclei".
  2. ^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
  3. ^ Specifically from thermal neutron fission of U-235, e.g. in a typical nuclear reactor.
  4. ^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
    "The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk248 with a half-life greater than 9 y. No growth of Cf248 was detected, and a lower limit for the β half-life can be set at about 104 y. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 y."
  5. ^ This is the heaviest nuclide with a half-life of at least four years before the "Sea of Instability".
  6. ^ Excluding those "classically stable" nuclides with half-lives significantly in excess of 232Th; e.g., while 113mCd has a half-life of only fourteen years, that of 113Cd is nearly eight quadrillion years.
  7. ^ "Universal Nuclide Chart". nucleonica.

The actinide or actinoid (IUPAC nomenclature) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.Strictly speaking, both actinium and lawrencium have been labeled as group 3 elements, but both elements are often included in any general discussion of the chemistry of the actinide elements. Actinium is the more often omitted of the two, because its placement as a group 3 element is somewhat more common in texts and for semantic reasons: since "actinide" means "like actinium", it has been argued that actinium cannot logically be an actinide, but IUPAC acknowledges its inclusion based on common usage.The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. All but one of the actinides are f-block elements, with the exception being either actinium or lawrencium. The series mostly corresponds to the filling of the 5f electron shell, although actinium and thorium lack any 5f electrons, and curium and lawrencium have the same number as the preceding element. In comparison with the lanthanides, also mostly f-block elements, the actinides show much more variable valence. They all have very large atomic and ionic radii and exhibit an unusually large range of physical properties. While actinium and the late actinides (from americium onwards) behave similarly to the lanthanides, the elements thorium, protactinium, and uranium are much more similar to transition metals in their chemistry, with neptunium and plutonium occupying an intermediate position.

All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors.

Of the actinides, primordial thorium and uranium occur naturally in substantial quantities. The radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores. The other actinides are purely synthetic elements. Nuclear weapons tests have released at least six actinides heavier than plutonium into the environment; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium, berkelium, californium, einsteinium and fermium.In presentations of the periodic table, the lanthanides and the actinides are customarily shown as two additional rows below the main body of the table, with placeholders or else a selected single element of each series (either lanthanum or lutetium, and either actinium or lawrencium, respectively) shown in a single cell of the main table, between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods).

Alkaline earth metal

The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure.Structurally, they have in common an outer s- electron shell which is full;

that is, this orbital contains its full complement of two electrons, which these elements readily lose to form cations with charge +2, and an oxidation state of +2.All the discovered alkaline earth metals occur in nature, although radium occurs only through the decay chain of uranium and thorium and not as a primordial element. Experiments have been conducted to attempt the synthesis of element 120, the next potential member of the group, but they have all met with failure.

Discovery of the neutron

The discovery of the neutron and its properties was central to the extraordinary developments in atomic physics in the first half of the 20th century. Early in the century, Ernest Rutherford developed a crude model of the atom, based on the gold foil experiment of Hans Geiger and Ernest Marsden. In this model, atoms had their mass and positive electric charge concentrated in a very small nucleus. By 1920 chemical isotopes had been discovered, the atomic masses had been determined to be (approximately) integer multiples of the mass of the hydrogen atom, and the atomic number had been identified as the charge on the nucleus. Throughout the 1920s, the nucleus was viewed as composed of combinations of protons and electrons, the two elementary particles known at the time, but that model presented several experimental and theoretical contradictions.The essential nature of the atomic nucleus was established with the discovery of the neutron by James Chadwick in 1932 and the determination that it was a new elementary particle, distinct from the proton.The uncharged neutron was immediately exploited as a new means to probe nuclear structure, leading to such discoveries as the creation of new radioactive elements by neutron irradiation (1934) and the fission of uranium atoms by neutrons (1938). The discovery of fission led to the creation of both nuclear power and weapons by the end of World War II. Both the proton and the neutron were presumed to be elementary particles until the 1960s, when they were determined to be composite particles built from quarks.

Gerhard W. Goetze

Gerhard Wilhelm Goetze (19 June 1930 – 17 January 2007) was a German-born Ph.D. researcher and inventor in Atomic physics. He was primarily known for his work on the moon-to-earth Apollo TV camera making live broadcast in both brilliant sunlight and pitch darkness possible. Goetze discovered the Secondary Electron Conduction (SEC) effect which amplified light through high-speed electrons deposited in thin film storage targets. The SEC tube was additionally used in ground-based astronomy, inspection of integrated circuits, electron-microscope-based biological tissue study, security, and night vision. Goetze received ten patents for his inventions.The images of the first man on the moon are recorded for eternity through the work of Goetze.In 1973 Goetze received a Franklin Institute Award, the Longstreth Medal established in 1890, for the conception and development of the SEC Tube, which played an important role in television, night surveillance and ultraviolet astronomical observations.In 1984 Goetze was awarded the Rudolf-Diesel-Medaille, an award by the German Institute for Inventions, for the applications of the Secondary Electron Conduction tube in industry.

Jiwchar Ganor

Jiwchar Ganor is a professor in the Department of Geological and Environmental Sciences at Ben-Gurion University of the Negev, and currently serves as Dean of the Faculty of Natural Sciences.

Period 7 element

A period 7 element is one of the chemical elements in the seventh row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The seventh period contains 32 elements, tied for the most with period 6, beginning with francium and ending with oganesson, the heaviest element currently discovered. As a rule, period 7 elements fill their 7s shells first, then their 5f, 6d, and 7p shells, in that order; however, there are exceptions, such as plutonium.


In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:

electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)

particle radiation, such as alpha radiation (α), beta radiation (β), and neutron radiation (particles of non-zero rest energy)

acoustic radiation, such as ultrasound, sound, and seismic waves (dependent on a physical transmission medium)

gravitational radiation, radiation that takes the form of gravitational waves, or ripples in the curvature of spacetime.Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules, and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth's atmosphere.

Gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The word "ionize" refers to the breaking of one or more electrons away from an atom, an action that requires the relatively high energies that these electromagnetic waves supply. Further down the spectrum, the non-ionizing lower energies of the lower ultraviolet spectrum cannot ionize atoms, but can disrupt the inter-atomic bonds which form molecules, thereby breaking down molecules rather than atoms; a good example of this is sunburn caused by long-wavelength solar ultraviolet. The waves of longer wavelength than UV in visible light, infrared and microwave frequencies cannot break bonds but can cause vibrations in the bonds which are sensed as heat. Radio wavelengths and below generally are not regarded as harmful to biological systems. These are not sharp delineations of the energies; there is some overlap in the effects of specific frequencies.The word radiation arises from the phenomenon of waves radiating (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that are applicable to all types of radiation. Because such radiation expands as it passes through space, and as its energy is conserved (in vacuum), the intensity of all types of radiation from a point source follows an inverse-square law in relation to the distance from its source. Like any ideal law, the inverse-square law approximates a measured radiation intensity to the extent that the source approximates a geometric point.


Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas (specifically the isotope radon-222). When radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence.

Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911.In nature, radium is found in uranium and (to a lesser extent) thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity. Currently, other than its use in nuclear medicine, radium has no commercial applications; formerly, it was used as a radioactive source for radioluminescent devices and also in radioactive quackery for its supposed curative powers. Today, these former applications are no longer in vogue because radium's toxicity has since become known, and less dangerous isotopes are used instead in radioluminescent devices.


Radium-223 (Ra-223, 223Ra) is an isotope of radium with an 11.4-day half-life, in contrast to the more common isotope radium-226, discovered by the Curies, which has a 1601-year half-life. The principal use of radium-223, as a radiopharmaceutical to treat metastatic cancers in bone, takes advantage of its chemical similarity to calcium, and the short range of the alpha radiation it emits.

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