Isotopes of protactinium
Encyclopedia
Protactinium
(Pa) has no stable isotopes. There are three naturally occurring isotopes, allowing a standard mass to be given.
Standard atomic mass: 231.03588(2) u
29 radioisotopes of protactinium have been characterized, with the most stable being 231Pa with a half-life
of 32,760 years, 233Pa with a half-life of 26.967 days, and 230Pa with a half-life of 17.4 days. All of the remaining radioactive isotopes have half-lives that are less than 1.6 days, and the majority of these have half-lives that are less than 1.8 seconds. This element also has 3 meta states, 217mPa (t½ 1.15 milliseconds), 229mPa (t½ 420 nanoseconds), and 234mPa (t½ 1.17 minutes).
The only naturally occurring isotopes are 231Pa, which occurs as an intermediate decay product of 235U
, 234Pa and 234mPa, both of which occur as intermediate decay products of 238U
. 231Pa makes up nearly all natural protactinium.
The primary decay mode for isotopes of Pa lighter than (and including) the most stable isotope 231Pa is alpha decay
, except for 228Pa to 230Pa, which primarily decay by electron capture to isotopes of thorium
. The primary mode for the heavier isotopes is beta minus (β-) decay
. The primary decay product
s of 231Pa and isotopes of Pa lighter than (and including 227Pa) are isotopes of actinium
and the primary decay products for the heavier isotopes of Pa are isotopes of uranium
.
s of 235U, 238U, or 232Th. It has a mass of 230.034541 grams/mole.
; the equilibrium
concentration in uranium ore is 46.55 231Pa per million 235U.
In nuclear reactor
s, it is one of the few long-lived radioactive actinide
s produced as a byproduct of the projected thorium fuel cycle
, as a result of (n,2n) reactions where a fast neutron removes a neutron
from 232Th or 232U, and can also be destroyed by neutron capture
though the cross section for this reaction is also low.
binding energy: 1759860 keV
beta decay energy: -382 keV
spin: 3/2-
mode of decay: alpha
to 227Ac, also others
possible parent nuclides: beta
from 231Th, EC
from 231U, alpha
from 235Np.
Protactinium
Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume...
(Pa) has no stable isotopes. There are three naturally occurring isotopes, allowing a standard mass to be given.
Standard atomic mass: 231.03588(2) u
29 radioisotopes of protactinium have been characterized, with the most stable being 231Pa with a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
of 32,760 years, 233Pa with a half-life of 26.967 days, and 230Pa with a half-life of 17.4 days. All of the remaining radioactive isotopes have half-lives that are less than 1.6 days, and the majority of these have half-lives that are less than 1.8 seconds. This element also has 3 meta states, 217mPa (t½ 1.15 milliseconds), 229mPa (t½ 420 nanoseconds), and 234mPa (t½ 1.17 minutes).
The only naturally occurring isotopes are 231Pa, which occurs as an intermediate decay product of 235U
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
, 234Pa and 234mPa, both of which occur as intermediate decay products of 238U
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
. 231Pa makes up nearly all natural protactinium.
The primary decay mode for isotopes of Pa lighter than (and including) the most stable isotope 231Pa is alpha decay
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
, except for 228Pa to 230Pa, which primarily decay by electron capture to isotopes of thorium
Isotopes of thorium
Although thorium has 6 naturally occurring isotopes, none of these isotopes are stable; however, one isotope, 232Th, is relatively stable, with a half-life of 14.05 billion years, considerably longer than the age of the earth, and even slightly longer than the generally-accepted age of the...
. The primary mode for the heavier isotopes is beta minus (β-) decay
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
. The primary decay product
Decay product
In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps...
s of 231Pa and isotopes of Pa lighter than (and including 227Pa) are isotopes of actinium
Isotopes of actinium
Actinium has no stable isotopes, thus a standard atomic mass cannot be given. There are 31 known isotopes, from 206Ac to 236Ac, and 2 isomers. Two isotopes are found in nature, 227Ac and 228Ac, as intermediate decay products of, respectively, 235U and 238U...
and the primary decay products for the heavier isotopes of Pa are isotopes of uranium
Isotopes of uranium
Uranium is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The average atomic mass of natural uranium is 238.02891 u...
.
Protactinium-230
Protactinium-230 has 139 neutrons and a half-life of 17.4 days. It undergoes beta-minus decay to 230U. It is not found in nature because its half-life is so short and it is not found in the decay chainDecay chain
In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
s of 235U, 238U, or 232Th. It has a mass of 230.034541 grams/mole.
Protactinium-231
Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series which starts with the primordial isotope uranium-235Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...
; the equilibrium
Secular equilibrium
In nuclear physics, secular equilibrium is a situation in which the quantity of a radioactive isotope remains constant because its production rate is equal to its decay rate.-Secular equilibrium in radioactive decay:...
concentration in uranium ore is 46.55 231Pa per million 235U.
In nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s, it is one of the few long-lived radioactive actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
s produced as a byproduct of the projected thorium fuel cycle
Thorium fuel cycle
The thorium fuel cycle is a nuclear fuel cycle that uses the naturally abundant isotope of thorium, , as the fertile material. In the reactor, is transmuted into the fissile artificial uranium isotope which is the nuclear fuel. Unlike natural uranium, natural thorium contains only trace amounts...
, as a result of (n,2n) reactions where a fast neutron removes a neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
from 232Th or 232U, and can also be destroyed by neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...
though the cross section for this reaction is also low.
binding energy: 1759860 keV
beta decay energy: -382 keV
spin: 3/2-
mode of decay: alpha
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
to 227Ac, also others
possible parent nuclides: beta
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
from 231Th, EC
Electron capture
Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino...
from 231U, alpha
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
from 235Np.
Protactinium-233
Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233 (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect Pa-233 from further neutron capture producing Pa-234 and U-234 which are not useful as fuel.Table
| nuclide symbol |
historic name |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-life | decay mode(s)Abbreviations: CD: Cluster decay Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy... EC: Electron capture Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... SF: Spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... |
daughter isotope(s)Stable isotopes in bold |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|---|
| excitation energy | ||||||||||
| 212Pa | 91 | 121 | 212.02320(8) | 8(5) ms [5.1(+61-19) ms] |
7+# | |||||
| 213Pa | 91 | 122 | 213.02111(8) | 7(3) ms [5.3(+40-16) ms] |
α Alpha decay Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less... |
209Ac | 9/2-# | |||
| 214Pa | 91 | 123 | 214.02092(8) | 17(3) ms | α | 210Ac | ||||
| 215Pa | 91 | 124 | 215.01919(9) | 14(2) ms | α | 211Ac | 9/2-# | |||
| 216Pa | 91 | 125 | 216.01911(8) | 105(12) ms | α (80%) | 212Ac | ||||
| β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... (20%) |
216Th | |||||||||
| 217Pa | 91 | 126 | 217.01832(6) | 3.48(9) ms | α | 213Ac | 9/2-# | |||
| 217mPa | 1860(7) keV | 1.08(3) ms | α | 213Ac | 29/2+# | |||||
| IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... (rare) |
217Pa | |||||||||
| 218Pa | 91 | 127 | 218.020042(26) | 0.113(1) ms | α | 214Ac | ||||
| 219Pa | 91 | 128 | 219.01988(6) | 53(10) ns | α | 215Ac | 9/2- | |||
| β+ (5×10−9%) | 219Th | |||||||||
| 220Pa | 91 | 129 | 220.02188(6) | 780(160) ns | α | 216Ac | 1-# | |||
| 221Pa | 91 | 130 | 221.02188(6) | 4.9(8) µs | α | 217Ac | 9/2- | |||
| 222Pa | 91 | 131 | 222.02374(8)# | 3.2(3) ms | α | 218Ac | ||||
| 223Pa | 91 | 132 | 223.02396(8) | 5.1(6) ms | α | 219Ac | ||||
| β+ (.001%) | 223Th | |||||||||
| 224Pa | 91 | 133 | 224.025626(17) | 844(19) ms | α (99.9%) | 220Ac | 5-# | |||
| β+ (.1%) | 224Th | |||||||||
| 225Pa | 91 | 134 | 225.02613(8) | 1.7(2) s | α | 221Ac | 5/2-# | |||
| 226Pa | 91 | 135 | 226.027948(12) | 1.8(2) min | α (74%) | 222Ac | ||||
| β+ (26%) | 226Th | |||||||||
| 227Pa | 91 | 136 | 227.028805(8) | 38.3(3) min | α (85%) | 223Ac | (5/2-) | |||
| EC Electron capture Electron capture is a process in which a proton-rich nuclide absorbs an inner atomic electron and simultaneously emits a neutrino... (15%) |
227Th | |||||||||
| 228Pa | 91 | 137 | 228.031051(5) | 22(1) h | β+ (98.15%) | 228Th | 3+ | |||
| α (1.85%) | 224Ac | |||||||||
| 229Pa | 91 | 138 | 229.0320968(30) | 1.50(5) d | EC (99.52%) | 229Th | (5/2+) | |||
| α (.48%) | 225Ac | |||||||||
| 229mPa | 11.6(3) keV | 420(30) ns | 3/2- | |||||||
| 230Pa | 91 | 139 | 230.034541(4) | 17.4(5) d | β+ (91.6%) | 230Th | (2-) | |||
| β- (8.4%) | 230U | |||||||||
| α (.00319%) | 226Ac | |||||||||
| 231Pa | Protoactinium | 91 | 140 | 231.0358840(24) | 3.276(11)×104 a | α | 227Ac | 3/2- | 1.0000Intermediate decay product Decay product In nuclear physics, a decay product is the remaining nuclide left over from radioactive decay. Radioactive decay often involves a sequence of steps... of 235U Uranium-235 - References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the... |
|
| CD Cluster decay Cluster decay is a type of nuclear decay in which a parent atomic nucleus with A nucleons and Z protons emits a cluster of Ne neutrons and Ze protons heavier than an alpha particle but lighter than a typical binary fission fragment Cluster decay (also named heavy particle radioactivity or heavy... (1.34×10−9%) |
207Tl 24Ne |
|||||||||
| SF Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... (3×10−10%) |
(various) | |||||||||
| CD (10−12%) | 208Pb 23F |
|||||||||
| 232Pa | 91 | 141 | 232.038592(8) | 1.31(2) d | β- | 232U | (2-) | |||
| EC (.003%) | 232Th | |||||||||
| 233Pa | 91 | 142 | 233.0402473(23) | 26.975(13) d | β- | 233U | 3/2- | |||
| 234Pa | Uranium Z | 91 | 143 | 234.043308(5) | 6.70(5) h | β- | 234U | 4+ | TraceIntermediate decay product of 238U Uranium-238 Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239... |
|
| SF (3×10−10%) | (various) | |||||||||
| 234mPa | Uranium X2 Brevium |
78(3) keV | 1.17(3) min | β- (99.83%) | 234U | (0-) | Trace | |||
| IT (.16%) | 234Pa | |||||||||
| SF (10−10%) | (various) | |||||||||
| 235Pa | 91 | 144 | 235.04544(5) | 24.44(11) min | β- | 235mU | (3/2-) | |||
| 236Pa | 91 | 145 | 236.04868(21) | 9.1(1) min | β- | 236U | 1(-) | |||
| β-, SF (6×10−8%) | (various) | |||||||||
| 237Pa | 91 | 146 | 237.05115(11) | 8.7(2) min | β- | 237U | (1/2+) | |||
| 238Pa | 91 | 147 | 238.05450(6) | 2.27(9) min | β- | 238U | (3-)# | |||
| β-, SF (2.6×10−6%) | (various) | |||||||||
| 239Pa | 91 | 148 | 239.05726(21)# | 1.8(5) h | β- | 239U | (3/2)(-#) | |||
| 240Pa | 91 | 149 | 240.06098(32)# | 2# min | β- | 240U | ||||