Aluminium-20

Properties and data of the isotope ²⁰Al.

Contents

Aluminium-20 is a radioisotope of the chemical element aluminium, which has 7 neutrons in its atomic nucleus in addition to the element-specific 13 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 20. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ²⁰Al is exclusively for academic purposes.

The proton-rich isotope was first identified in 2025 by the detection of its decay products; the nucleus decays with sequential 1p-2p emission via the intermediate state of magnesium-19, releasing a total of three protons to form neon-17 with a 3p decay energy of 1.93+0.12-0.10 MeV [1].

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

General data

Name of the isotope:Aluminium-20; Al-20Symbol:²⁰Al or 2013AlMass number A:20 (= number of nucleons)Atomic number Z:13 (= number of protons)Neutrons N:7Isotopic mass:20.04326(13) u (atomic weight of Aluminium-20)Nuclide mass:20.0361285 u (calculated nuclear mass without electrons)Mass excess:40.29643 MeVMass defect:0.119119828 u (per nucleus)Nuclear binding energy:110.95940506 MeV (per nucleus)
5.54797025 MeV (average binding energy per nucleon)Half-life:1.1 zsDecay constant λ:6.301338005090 × 10⁺²⁰ s^-1Specific activity α:1.897377253636 × 10⁺⁴³ Bq g^-1
5.128046631449 × 10⁺³² Ci g^-1Spin and parity:
(nuclear angular momentum)(1-)Mirror nucleus:Nitrogen-20Year of discovery:2024

Radioactive Decay

Half-life T_½ = 1.1 zs respectively 1.1 × 10^-21 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
p	¹⁹Mg	100 %

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 7) and isobaric (same nucleon number A = 20) with Aluminium-20. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 7	Isobar A = 20
2	⁹He
3	¹⁰Li
4	¹¹Be
5	¹²B	²⁰B
6	¹³C	²⁰C
7	¹⁴N	²⁰N
8	¹⁵O	²⁰O
9	¹⁶F	²⁰F
10	¹⁷Ne	²⁰Ne
11	¹⁸Na	²⁰Na
12	¹⁹Mg	²⁰Mg
13	²⁰Al	²⁰Al