This article needs additional citations for
verification. (May 2018) |
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Standard atomic weight Ar°(Be) | |||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Beryllium (4Be) has 11 known
isotopes and 3 known
isomers, but only one of these isotopes (9
Be
) is stable and a
primordial nuclide. As such, beryllium is considered a
monoisotopic element. It is also a
mononuclidic element, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (
standard atomic weight is 9.0121831(5)). Beryllium is unique as being the only monoisotopic element with both an even number of protons and an odd number of neutrons. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons.
Of the 10
radioisotopes of beryllium, the most stable are 10
Be
with a half-life of 1.387(12) million years
[nb 1] and 7
Be
with a half-life of 53.22(6) d. All other radioisotopes have half-lives under 15 s, most under 30 milliseconds. The least stable isotope is 16
Be
, with a half-life of 650(130) yoctoseconds.
The 1:1
neutron–proton ratio seen in stable isotopes of many light elements (up to
oxygen, and in elements with even atomic number up to
calcium) is prevented in beryllium by the extreme instability of
8
Be
toward
alpha decay, which is favored due to the extremely tight binding of
4
He
nuclei. The half-life for the decay of 8
Be
is only 81.9(3.7) attoseconds.
Beryllium is prevented from having a stable isotope with 4 protons and 6 neutrons by the very large mismatch in neutron–proton ratio for such a light element. Nevertheless, this isotope,
10
Be
, has a half-life of 1.387(12) million years
[nb 1], which indicates unusual stability for a light isotope with such a large neutron/proton imbalance. Other possible beryllium isotopes have even more severe mismatches in neutron and proton number, and thus are even less stable.
Most 9
Be
in the universe is thought to be formed by cosmic ray nucleosynthesis from
cosmic ray spallation in the period between the
Big Bang and the formation of the Solar System. The isotopes 7
Be
, with a half-life of 53.22(6) d, and 10
Be
are both
cosmogenic nuclides because they are made on a recent timescale in the Solar System by spallation,
[4] like
14
C
.
Nuclide [n 1] |
Z | N |
Isotopic mass (
Da)
[5] [n 2] [n 3] |
Half-life
[1] [ resonance width] |
Decay mode [1] [n 4] |
Daughter isotope [n 5] |
Spin and parity [1] [n 6] |
Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion [1] | Range of variation | |||||||||||||||||
5 Be [n 7] |
4 | 1 | 5.03987(215)# | p ? [n 8] | 4 Li ? |
(1/2+)# | |||||||||||||
6 Be |
4 | 2 | 6.019726(6) | 5.0(3) zs 91.6(5.6) keV] |
2p | 4 He |
0+ | ||||||||||||
7 Be [n 9] |
4 | 3 | 7.01692871(8) | 53.22(6) d | ε | 7 Li |
3/2− | Trace [n 10] | |||||||||||
8 Be [n 11] |
4 | 4 | 8.00530510(4) | 81.9(3.7) as 5.58(25) eV] |
α [n 12] | 4 He |
0+ | ||||||||||||
8m Be |
16626(3) keV | α | 4 He |
2+ | |||||||||||||||
9 Be |
4 | 5 | 9.01218306(8) | Stable | 3/2− | 1 | |||||||||||||
9m Be |
14390.3(1.7) keV | 1.25(10) as 367(30) eV] |
3/2− | ||||||||||||||||
10 Be |
4 | 6 | 10.01353469(9) | 1.387(12)×106 y [nb 1] | β− | 10 B |
0+ | Trace [n 10] | |||||||||||
11 Be [n 13] |
4 | 7 | 11.02166108(26) | 13.76(7) s | β− (96.7(1)%) | 11 B |
1/2+ | ||||||||||||
β−α (3.3(1)%) | 7 Li | ||||||||||||||||||
β−p (0.0013(3)%) | 10 Be | ||||||||||||||||||
11m Be |
21158(20) keV | 0.93(13) zs 500(75) keV] |
IT ? [n 8] | 11 Be ? |
3/2− | ||||||||||||||
12 Be |
4 | 8 | 12.0269221(20) | 21.46(5) ms | β− (99.50(3)%) | 12 B |
0+ | ||||||||||||
β−n (0.50(3)%) | 11 B | ||||||||||||||||||
12m Be |
2251(1) keV | 233(7) ns | IT | 12 Be |
0+ | ||||||||||||||
13 Be |
4 | 9 | 13.036135(11) | 1.0(7) zs | n ? [n 8] | 12 Be ? |
(1/2−) | ||||||||||||
13m Be |
1500(50) keV | (5/2+) | |||||||||||||||||
14 Be [n 14] |
4 | 10 | 14.04289(14) | 4.53(27) ms | β−n (86(6)%) | 13 B |
0+ | ||||||||||||
β− (> 9.0(6.3)%) | 14 B | ||||||||||||||||||
β−2n (5(2)%) | 12 B | ||||||||||||||||||
β−t (0.02(1)%) | 11 Be | ||||||||||||||||||
β−α (< 0.004%) | 10 Li | ||||||||||||||||||
14m Be |
1520(150) keV | (2+) | |||||||||||||||||
15 Be |
4 | 11 | 15.05349(18) | 790(270) ys | n | 14 Be |
(5/2+) | ||||||||||||
16 Be |
4 | 12 | 16.06167(18) | 650(130) ys 0.73(18) MeV] |
2n | 14 Be |
0+ | ||||||||||||
This table header & footer: |
EC: | Electron capture |
IT: | Isomeric transition |
n: | Neutron emission |
p: | Proton emission |
Beryllium-7 is an isotope with a half-life of 53.3 days that is generated naturally as a cosmogenic nuclide.
[4] The rate at which the short-lived 7
Be
is transferred from the air to the ground is controlled in part by the weather. 7
Be
decay in the Sun is one of the sources of
solar neutrinos, and the first type ever detected using the
Homestake experiment. Presence of 7
Be
in sediments is often used to establish that they are fresh, i.e. less than about 3–4 months in age, or about two half-lives of 7
Be
.
[6]
Beryllium-10 has a half-life of 1.39×106 y, and decays by beta decay to stable boron-10 with a maximum energy of 556.2 keV. [7] [8] It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen. [9] [10] [11] 10Be and its daughter product have been used to examine soil erosion, soil formation from regolith, the development of lateritic soils and the age of ice cores. [12] 10Be is a significant isotope used as a proxy data measure for cosmogenic nuclides to characterize solar and extra-solar attributes of the past from terrestrial samples. [13]
Most isotopes of beryllium within the proton/neutron
drip lines decay via
beta decay and/or a combination of beta decay and
alpha decay or neutron emission. However, 7
Be
decays only via
electron capture, a phenomenon to which its unusually long half-life may be attributed. Notably, its half-life can be artificially lowered by 0.83% via
endohedral enclosure (7Be@C60).
[14] Also anomalous is 8
Be
, which decays via alpha decay to 4
He
. This alpha decay is often considered fission, which would be able to account for its extremely short half-life.
This article needs additional citations for
verification. (May 2018) |
| |||||||||||||||||||||||||||||||
Standard atomic weight Ar°(Be) | |||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Beryllium (4Be) has 11 known
isotopes and 3 known
isomers, but only one of these isotopes (9
Be
) is stable and a
primordial nuclide. As such, beryllium is considered a
monoisotopic element. It is also a
mononuclidic element, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (
standard atomic weight is 9.0121831(5)). Beryllium is unique as being the only monoisotopic element with both an even number of protons and an odd number of neutrons. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons.
Of the 10
radioisotopes of beryllium, the most stable are 10
Be
with a half-life of 1.387(12) million years
[nb 1] and 7
Be
with a half-life of 53.22(6) d. All other radioisotopes have half-lives under 15 s, most under 30 milliseconds. The least stable isotope is 16
Be
, with a half-life of 650(130) yoctoseconds.
The 1:1
neutron–proton ratio seen in stable isotopes of many light elements (up to
oxygen, and in elements with even atomic number up to
calcium) is prevented in beryllium by the extreme instability of
8
Be
toward
alpha decay, which is favored due to the extremely tight binding of
4
He
nuclei. The half-life for the decay of 8
Be
is only 81.9(3.7) attoseconds.
Beryllium is prevented from having a stable isotope with 4 protons and 6 neutrons by the very large mismatch in neutron–proton ratio for such a light element. Nevertheless, this isotope,
10
Be
, has a half-life of 1.387(12) million years
[nb 1], which indicates unusual stability for a light isotope with such a large neutron/proton imbalance. Other possible beryllium isotopes have even more severe mismatches in neutron and proton number, and thus are even less stable.
Most 9
Be
in the universe is thought to be formed by cosmic ray nucleosynthesis from
cosmic ray spallation in the period between the
Big Bang and the formation of the Solar System. The isotopes 7
Be
, with a half-life of 53.22(6) d, and 10
Be
are both
cosmogenic nuclides because they are made on a recent timescale in the Solar System by spallation,
[4] like
14
C
.
Nuclide [n 1] |
Z | N |
Isotopic mass (
Da)
[5] [n 2] [n 3] |
Half-life
[1] [ resonance width] |
Decay mode [1] [n 4] |
Daughter isotope [n 5] |
Spin and parity [1] [n 6] |
Natural abundance (mole fraction) | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion [1] | Range of variation | |||||||||||||||||
5 Be [n 7] |
4 | 1 | 5.03987(215)# | p ? [n 8] | 4 Li ? |
(1/2+)# | |||||||||||||
6 Be |
4 | 2 | 6.019726(6) | 5.0(3) zs 91.6(5.6) keV] |
2p | 4 He |
0+ | ||||||||||||
7 Be [n 9] |
4 | 3 | 7.01692871(8) | 53.22(6) d | ε | 7 Li |
3/2− | Trace [n 10] | |||||||||||
8 Be [n 11] |
4 | 4 | 8.00530510(4) | 81.9(3.7) as 5.58(25) eV] |
α [n 12] | 4 He |
0+ | ||||||||||||
8m Be |
16626(3) keV | α | 4 He |
2+ | |||||||||||||||
9 Be |
4 | 5 | 9.01218306(8) | Stable | 3/2− | 1 | |||||||||||||
9m Be |
14390.3(1.7) keV | 1.25(10) as 367(30) eV] |
3/2− | ||||||||||||||||
10 Be |
4 | 6 | 10.01353469(9) | 1.387(12)×106 y [nb 1] | β− | 10 B |
0+ | Trace [n 10] | |||||||||||
11 Be [n 13] |
4 | 7 | 11.02166108(26) | 13.76(7) s | β− (96.7(1)%) | 11 B |
1/2+ | ||||||||||||
β−α (3.3(1)%) | 7 Li | ||||||||||||||||||
β−p (0.0013(3)%) | 10 Be | ||||||||||||||||||
11m Be |
21158(20) keV | 0.93(13) zs 500(75) keV] |
IT ? [n 8] | 11 Be ? |
3/2− | ||||||||||||||
12 Be |
4 | 8 | 12.0269221(20) | 21.46(5) ms | β− (99.50(3)%) | 12 B |
0+ | ||||||||||||
β−n (0.50(3)%) | 11 B | ||||||||||||||||||
12m Be |
2251(1) keV | 233(7) ns | IT | 12 Be |
0+ | ||||||||||||||
13 Be |
4 | 9 | 13.036135(11) | 1.0(7) zs | n ? [n 8] | 12 Be ? |
(1/2−) | ||||||||||||
13m Be |
1500(50) keV | (5/2+) | |||||||||||||||||
14 Be [n 14] |
4 | 10 | 14.04289(14) | 4.53(27) ms | β−n (86(6)%) | 13 B |
0+ | ||||||||||||
β− (> 9.0(6.3)%) | 14 B | ||||||||||||||||||
β−2n (5(2)%) | 12 B | ||||||||||||||||||
β−t (0.02(1)%) | 11 Be | ||||||||||||||||||
β−α (< 0.004%) | 10 Li | ||||||||||||||||||
14m Be |
1520(150) keV | (2+) | |||||||||||||||||
15 Be |
4 | 11 | 15.05349(18) | 790(270) ys | n | 14 Be |
(5/2+) | ||||||||||||
16 Be |
4 | 12 | 16.06167(18) | 650(130) ys 0.73(18) MeV] |
2n | 14 Be |
0+ | ||||||||||||
This table header & footer: |
EC: | Electron capture |
IT: | Isomeric transition |
n: | Neutron emission |
p: | Proton emission |
Beryllium-7 is an isotope with a half-life of 53.3 days that is generated naturally as a cosmogenic nuclide.
[4] The rate at which the short-lived 7
Be
is transferred from the air to the ground is controlled in part by the weather. 7
Be
decay in the Sun is one of the sources of
solar neutrinos, and the first type ever detected using the
Homestake experiment. Presence of 7
Be
in sediments is often used to establish that they are fresh, i.e. less than about 3–4 months in age, or about two half-lives of 7
Be
.
[6]
Beryllium-10 has a half-life of 1.39×106 y, and decays by beta decay to stable boron-10 with a maximum energy of 556.2 keV. [7] [8] It is formed in the Earth's atmosphere mainly by cosmic ray spallation of nitrogen and oxygen. [9] [10] [11] 10Be and its daughter product have been used to examine soil erosion, soil formation from regolith, the development of lateritic soils and the age of ice cores. [12] 10Be is a significant isotope used as a proxy data measure for cosmogenic nuclides to characterize solar and extra-solar attributes of the past from terrestrial samples. [13]
Most isotopes of beryllium within the proton/neutron
drip lines decay via
beta decay and/or a combination of beta decay and
alpha decay or neutron emission. However, 7
Be
decays only via
electron capture, a phenomenon to which its unusually long half-life may be attributed. Notably, its half-life can be artificially lowered by 0.83% via
endohedral enclosure (7Be@C60).
[14] Also anomalous is 8
Be
, which decays via alpha decay to 4
He
. This alpha decay is often considered fission, which would be able to account for its extremely short half-life.