Antimony-121m

Properties and data of the isotope ^121mSb.

Contents

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

General data

Name of the isotope:Antimony-121m; Sb-121mSymbol:^121mSb or 121m51SbMass number A:121 (= number of nucleons)Atomic number Z:51 (= number of protons)Neutrons N:70Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):1.3725490196078 (= neutron-proton ratio)Neutron excess (N-Z):19Excitation energy:2721.5+x keVIsotopic mass:120.90381(2) u (atomic weight of Antimony-121m)Nuclide mass:120.8758341 u (calculated nuclear mass without electrons)Mass excess:-89.60041 MeVMass defect:1.101810752 u (per nucleus)Nuclear binding energy:1026.33010462 MeV (per nucleus)
8.48206698 MeV (average binding energy per nucleon)Half-life:179(6) μsDecay constant λ:3872.3306176533 s^-1Specific activity α:1.943310036312 × 10⁺²⁵ Bq g^-1
5.252189287331 × 10⁺¹⁴ Ci g^-1Spin and parity:
(nuclear angular momentum)(25/2)

Radioactive Decay

Half-life T_½ = 179(6) μs respectively 1.79 × 10^-4 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹²¹Sb	100 %

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
¹²¹Sb		stable	5/2+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 70) and isobaric (same nucleon number A = 121) with Antimony-121m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 70	Isobar A = 121
39	¹⁰⁹Y
40	¹¹⁰Zr
41	¹¹¹Nb
42	¹¹²Mo
43	¹¹³Tc	¹²¹Tc
44	¹¹⁴Ru	¹²¹Ru
45	¹¹⁵Rh	¹²¹Rh
46	¹¹⁶Pd	¹²¹Pd
47	¹¹⁷Ag	¹²¹Ag
48	¹¹⁸Cd	¹²¹Cd
49	¹¹⁹In	¹²¹In
50	¹²⁰Sn	¹²¹Sn
51	¹²¹Sb	¹²¹Sb
52	¹²²Te	¹²¹Te
53	¹²³I	¹²¹I
54	¹²⁴Xe	¹²¹Xe
55	¹²⁵Cs	¹²¹Cs
56	¹²⁶Ba	¹²¹Ba
57	¹²⁷La	¹²¹La
58	¹²⁸Ce	¹²¹Ce
59	¹²⁹Pr	¹²¹Pr
60	¹³⁰Nd
61	¹³¹Pm
62	¹³²Sm
63	¹³³Eu
64	¹³⁴Gd
65	¹³⁵Tb