Carbon-21

Properties and data of the isotope ²¹C.

Contents

Carbon-21 is a hypothetical radioisotope of the chemical element carbon, which has 15 neutrons in its atomic nucleus in addition to the element-specific 6 protons.

Despite some theoretical considerations, the radioactive isotope has not yet been experimentally proven. The data given here are calculated values.

See also: List of individual Carbon isotopes (and general data sources).

General data

Name of the isotope:Carbon-21; C-21Symbol:²¹C or 216CMass number A:21 (= number of nucleons)Atomic number Z:6 (= number of protons)Neutrons N:15Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):2.5 (= neutron-proton ratio)Neutron excess (N-Z):9Isotopic mass:21.04900(64) u (atomic weight of Carbon-21)Nuclide mass:21.0457085 u (calculated nuclear mass without electrons)Mass excess:45.64321 MeVMass defect:0.127923932 u (per nucleus)Nuclear binding energy:119.16037511 MeV (per nucleus)
5.67430358 MeV (average binding energy per nucleon)Half-life:< 30 nsDecay constant λ:23104906.018665 s^-1Specific activity α:6.625761838095 × 10⁺²⁹ Bq g^-1
1.790746442728 × 10⁺¹⁹ Ci g^-1Spin and parity:
(nuclear angular momentum)(1/2+)Year of discovery:-

Radioactive Decay

Half-life T_½ = < 30 ns respectively 3 × 10^-8 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
n	²⁰C

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 15) and isobaric (same nucleon number A = 21) with Carbon-21. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 15	Isobar A = 21
5	²⁰B	²¹B
6	²¹C	²¹C
7	²²N	²¹N
8	²³O	²¹O
9	²⁴F	²¹F
10	²⁵Ne	²¹Ne
11	²⁶Na	²¹Na
12	²⁷Mg	²¹Mg
13	²⁸Al	²¹Al
14	²⁹Si
15	³⁰P
16	³¹S
17	³²Cl
18	³³Ar
19	³⁴K
20	³⁵Ca
21	³⁶Sc

External data and identifiers

Adopted Levels, Gammas:NuDat 21C

Literature and References

[1] - S. Mosby et al.:
Search for ²¹C and constraints on ²²C.
In: Nuclear Physics A, 909, (2013), DOI 10.1016/j.nuclphysa.2013.04.004.

[2] - Tokuro Fukuia, Kazuyuki Ogata:
Investigation of the unbound ²¹C nucleus via transfer reaction.
In: EPJ Web of Conferences 66, 03031, (2014), DOI 10.1051/epjconf/20146603031.