Selenium-78

Properties and data of the isotope ⁷⁸Se.

Contents

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

General data

Name of the isotope:Selenium-78; Se-78Symbol:⁷⁸Se or 7834SeMass number A:78 (= number of nucleons)Atomic number Z:34 (= number of protons)Neutrons N:44Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.2941176470588 (= neutron-proton ratio)Neutron excess (N-Z):10Isotopic mass:77.917309(2) u (atomic weight of Selenium-78)Nuclide mass:77.8986579 u (calculated nuclear mass without electrons)Mass excess:-77.02617 MeVMass defect:0.729998392 u (per nucleus)Nuclear binding energy:679.98912216 MeV (per nucleus)
8.71780926 MeV (average binding energy per nucleon)Separation energy:S_N = 10.49777(17) MeV (first neutron)
S_P = 10.3986(17) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)0+Charge radius:4.1406(17) femtometer fmYear of discovery:1922

Parent Nuclides

Direct parent isotopes are: ⁷⁸Br, ⁷⁸As.

Occurrence

Comparison of the natural Selenium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Selenium Isotopic mixture	78.971 u	100 %
Isotope ⁷⁴Se	73.9224759(1) u	0.86(3) %	stable	0+
Isotope ⁷⁶Se	75.9192137(2) u	9.23(7) %	stable	0+
Isotope ⁷⁸Se	77.917309(2) u	23.69(22) %	stable	0+
Isotope ⁸⁰Se	79.916522(8) u	49.80(36) %	stable	0+
Isotope ⁸²Se	81.916700(9) u	8.82(15) %	9.39(17) × 10¹⁹ a	0+
Isotope ⁷⁷Se	76.91991415(7) u	7.60(7) %	stable	1/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 44) and isobaric (same nucleon number A = 78) with Selenium-78. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 44	Isobar A = 78
22	⁶⁶Ti
23	⁶⁷V
24	⁶⁸Cr
25	⁶⁹Mn
26	⁷⁰Fe
27	⁷¹Co
28	⁷²Ni	⁷⁸Ni
29	⁷³Cu	⁷⁸Cu
30	⁷⁴Zn	⁷⁸Zn
31	⁷⁵Ga	⁷⁸Ga
32	⁷⁶Ge	⁷⁸Ge
33	⁷⁷As	⁷⁸As
34	⁷⁸Se	⁷⁸Se
35	⁷⁹Br	⁷⁸Br
36	⁸⁰Kr	⁷⁸Kr
37	⁸¹Rb	⁷⁸Rb
38	⁸²Sr	⁷⁸Sr
39	⁸³Y	⁷⁸Y
40	⁸⁴Zr	⁷⁸Zr
41	⁸⁵Nb
42	⁸⁶Mo
43	⁸⁷Tc
44	⁸⁸Ru
45	⁸⁹Rh
46	⁹⁰Pd