Silicon-40

Properties and data of the isotope ⁴⁰Si.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Silicon-40 is a radioisotope of the chemical element silicon, which has 26 neutrons in its atomic nucleus in addition to the element-specific 14 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 40. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ⁴⁰Si is exclusively for academic purposes.

The discovery of the neutron-rich isotope was first reported in 1989. Silicon-40 was observed when a tantalum sample was irradiated with calcium-48 with an energy of 55 MeV/u [1].

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

General data

Name of the isotope:Silicon-40; Si-40Symbol:⁴⁰Si or 4014SiMass number A:40 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:26Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.8571428571429 (= neutron-proton ratio)Neutron excess (N-Z):12Isotopic mass:40.00608(13) u (atomic weight of Silicon-40)Nuclide mass:39.9984 u (calculated nuclear mass without electrons)Mass excess:5.66348 MeVMass defect:0.328758264 u (per nucleus)Nuclear binding energy:306.23635037 MeV (per nucleus)
7.65590876 MeV (average binding energy per nucleon)Separation energy:S_N = 4.725(182) MeV (first neutron)
S_P = 23.112(324) MeV (first proton)Half-life:31.2(26) msDecay constant λ:22.216255787178 s^-1Specific activity α:3.344735543269 × 10⁺²³ Bq g^-1
9039825792619.5 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Year of discovery:1989

Radioactive Decay

Half-life T_½ = 31.2(26) ms respectively 3.12 × 10^-2 seconds s.

Decay mode	Daughter	Probability	Decay energy
β^-	⁴⁰P	62 %	13.81(15) MeV
β^-, n	³⁹P	38 %	10.37(166) MeV
β^-, 2n ?

Parent Nuclides

Direct parent isotope is: ⁴⁰Al.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 26) and isobaric (same nucleon number A = 40) with Silicon-40. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 26	Isobar A = 40
11	³⁷Na
12	³⁸Mg	⁴⁰Mg
13	³⁹Al	⁴⁰Al
14	⁴⁰Si	⁴⁰Si
15	⁴¹P	⁴⁰P
16	⁴²S	⁴⁰S
17	⁴³Cl	⁴⁰Cl
18	⁴⁴Ar	⁴⁰Ar
19	⁴⁵K	⁴⁰K
20	⁴⁶Ca	⁴⁰Ca
21	⁴⁷Sc	⁴⁰Sc
22	⁴⁸Ti	⁴⁰Ti
23	⁴⁹V	⁴⁰V
24	⁵⁰Cr
25	⁵¹Mn
26	⁵²Fe
27	⁵³Co
28	⁵⁴Ni
29	⁵⁵Cu
30	⁵⁶Zn