Phosphorus-42

Properties and data of the isotope ⁴²P.

Contents

Phosphorus-42 is a radioisotope of the chemical element phosphorus, which has 27 neutrons in its atomic nucleus in addition to the element-specific 15 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 42. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁴²P is exclusively for academic purposes.

According to a report from 1979, the neutron-rich isotope phosphorus-42 was discovered during the fragmentation of calcium-48 ions - accelerated to 212 MeV per nucleon - on a Be target [1].

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

General data

Name of the isotope:Phosphorus-42; P-42Symbol:⁴²P or 4215PMass number A:42 (= number of nucleons)Atomic number Z:15 (= number of protons)Neutrons N:27Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.8 (= neutron-proton ratio)Neutron excess (N-Z):12Isotopic mass:42.00117(10) u (atomic weight of Phosphorus-42)Nuclide mass:41.9929414 u (calculated nuclear mass without electrons)Mass excess:1.08985 MeVMass defect:0.350158212 u (per nucleus)Nuclear binding energy:326.17027353 MeV (per nucleus)
7.76595889 MeV (average binding energy per nucleon)Separation energy:S_N = 2.000(153) MeV (first neutron)
S_P = 19.397(315) MeV (first proton)Half-life:48.5(15) msDecay constant λ:14.291694444535 s^-1Specific activity α:2.049204692194 × 10⁺²³ Bq g^-1
5538391059984.9 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:1979

Radioactive Decay

Half-life T_½ = 48.5(15) ms respectively 4.85 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy
β^-	⁴²S	50 %	18.73(10) MeV
β^-, n	⁴¹S	50(20) %	12.029(95) MeV
β^-, 2n ?	⁴⁰S

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 27) and isobaric (same nucleon number A = 42) with Phosphorus-42. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 27	Isobar A = 42
11	³⁸Na
12	³⁹Mg
13	⁴⁰Al	⁴²Al
14	⁴¹Si	⁴²Si
15	⁴²P	⁴²P
16	⁴³S	⁴²S
17	⁴⁴Cl	⁴²Cl
18	⁴⁵Ar	⁴²Ar
19	⁴⁶K	⁴²K
20	⁴⁷Ca	⁴²Ca
21	⁴⁸Sc	⁴²Sc
22	⁴⁹Ti	⁴²Ti
23	⁵⁰V	⁴²V
24	⁵¹Cr	⁴²Cr
25	⁵²Mn	⁴²Mn
26	⁵³Fe
27	⁵⁴Co
28	⁵⁵Ni
29	⁵⁶Cu
30	⁵⁷Zn
31	⁵⁸Ga
32	⁵⁹Ge

External data and identifiers

Adopted Levels, Gammas:NuDat 42P

Literature and References

[1] - G. D. Westfall, T. J. M. Symons, D. E. Greiner et al.:
Production of Neutron-Rich Nuclides by Fragmentation of 212-MeV/amu ⁴⁸Ca.
In: Physical Review Letters,43, 1859, (1979), DOI 10.1103/PhysRevLett.43.1859.