Mendelevium-258

Properties and data of the isotope ²⁵⁸Md.

Contents

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

General data

Name of the isotope:Mendelevium-258; Md-258Symbol:²⁵⁸Md or 258101MdMass number A:258 (= number of nucleons)Atomic number Z:101 (= number of protons)Neutrons N:157Nucleon pairing (Z - N):odd - oddNuclear ratio (N/Z ratio):1.5544554455446 (= neutron-proton ratio)Neutron excess (N-Z):56Isotopic mass:258.098430(5) u (atomic weight of Mendelevium-258)Nuclide mass:258.0430317 u (calculated nuclear mass without electrons)Mass excess:91.68695 MeVMass defect:2.052290044 u (per nucleus)Nuclear binding energy:1911.69586225 MeV (per nucleus)
7.40967388 MeV (average binding energy per nucleon)Separation energy:S_N = 5.378(4) MeV (first neutron)
S_P = 4.192(6) MeV (first proton)Half-life:51.50(29) dDecay constant λ:1.557774138259 × 10^-7 s^-1Specific activity α:3.636098949056 × 10⁺¹⁴ Bq g^-1
9827.2944569089 Ci g^-1Spin and parity:
(nuclear angular momentum)(8-)Year of discovery:1970

Radioactive Decay

Half-life T_½ = 51.50(29) d respectively 4.44960 × 10⁶ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²⁵⁴Es	~100 %	7.2713(19) MeV
SZ, ε	div	≤ 0.003 %

Occurrence

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

	Atomic Mass m_a	Quantity	Half-life	Spin
Mendelevium Isotopic mixture	258.098432704 u	100 %
Isotope ²⁵⁸Md	258.098430(5) u	100 %	51.50(29) d	(8-)

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
^258mMd	+x keV	57.0(9) min	(1-)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 157) and isobaric (same nucleon number A = 258) with Mendelevium-258. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 157	Isobar A = 258
97	²⁵⁴Bk
98	²⁵⁵Cf
99	²⁵⁶Es
100	²⁵⁷Fm	²⁵⁸Fm
101	²⁵⁸Md	²⁵⁸Md
102	²⁵⁹No	²⁵⁸No
103	²⁶⁰Lr	²⁵⁸Lr
104	²⁶¹Rf	²⁵⁸Rf
105	²⁶²Db	²⁵⁸Db
106	²⁶³Sg	²⁵⁸Sg
107	²⁶⁴Bh
108	²⁶⁵Hs
109	²⁶⁶Mt
110	²⁶⁷Ds