Isotopes of mendelevium

Mendelevium (₁₀₁Md) is a synthetic element, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁵⁶Md (which was also the first isotope of any element produced one atom at a time) in 1955. There are 17 known radioisotopes, ranging in atomic mass from ²⁴⁴Md to ²⁶⁰Md, and 10 isomers. The longest-lived isotope is ²⁵⁸Md with a half-life of 51.6 days, and the longest-lived isomer is ^258mMd with a half-life of 57 minutes.

Quick facts Main isotopes, Decay ...

Isotopes of mendelevium (₁₀₁Md)

Main isotopes^[1]			Decay
Isotope	abundance	half-life (t_1/2)	mode	product
²⁵⁶Md	synth	77.7 min	ε	²⁵⁶Fm
²⁵⁶Md	synth	77.7 min	α	²⁵²Es
²⁵⁷Md	synth	5.52 h	ε	²⁵⁷Fm
²⁵⁷Md	synth	5.52 h	α	²⁵³Es
²⁵⁸Md	synth	51.6 d	α	²⁵⁴Es
²⁵⁹Md	synth	1.60 h	SF	–
²⁶⁰Md	synth	27.8 d	SF	–

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List of isotopes

More information Nuclide, Z ...

Nuclide ^{[n 1]}	Z	N	Isotopic mass (Da)^[2] ^{[n 2]}^{[n 3]}	Discovery year^[3]^[4]	Half-life^[1]	Decay mode^[1] ^{[n 4]}	Daughter isotope	Spin and parity^[1] ^{[n 5]}^{[n 6]}
Nuclide ^{[n 1]}	Excitation energy^{[n 6]}			Discovery year^[3]^[4]	Half-life^[1]	Decay mode^[1] ^{[n 4]}	Daughter isotope	Spin and parity^[1] ^{[n 5]}^{[n 6]}
²⁴⁴Md^{[n 7]}	101	143	244.08116(40)#	2020	0.30+0.19 −0.09 s [0.36(14) s]	α	²⁴⁰Es	3+#
²⁴⁴Md^{[n 7]}	101	143	244.08116(40)#	2020	0.30+0.19 −0.09 s [0.36(14) s]	β⁺, SF (<14%)	(various)	3+#
^244mMd^{[n 7]}	200(150)# keV			(2020)^{[n 8]}	~9 μs	IT	²⁴⁴Md	7+#
²⁴⁵Md	101	144	245.08086(28)#	1996	0.38(10) s	α	²⁴¹Es	(7/2−)
^245mMd^{[n 9]}	100(100)# keV			1996	0.90(25) ms	SF	(various)	1/2−#
²⁴⁶Md	101	145	246.08171(28)#	1996	0.92(18) s	α	²⁴²Es	1−#
^246mMd^{[n 9]}	60(60) keV			2010	4.4(8) s	β⁺ (~67%)	²⁴⁶Fm	4−#
						α (<23%)	²⁴²Es
						β⁺, SF (>10%)	(various)
²⁴⁷Md	101	146	247.08152(22)#	1981	1.20(12) s^[6]	α (99.14%)	²⁴³Es	(7/2−)
²⁴⁷Md	101	146	247.08152(22)#	1981	1.20(12) s^[6]	SF (0.86%)^[6]	(various)	(7/2−)
^247mMd^[6]	153 keV			2010	0.23(3) s	α (80%)	²⁴³Es	(1/2−)
^247mMd^[6]	153 keV			2010	0.23(3) s	SF (20%)	(various)	(1/2−)
²⁴⁸Md	101	147	248.08261(20)#	1973	7(3) s	β⁺ (80%)	²⁴⁸Fm
						α (20%)	²⁴⁴Es
						β⁺, SF (<0.05%)	(various)
²⁴⁹Md	101	148	249.08286(18)	1973	25.6(9) s	α (75%)	²⁴⁵Es	(7/2−)
²⁴⁹Md	101	148	249.08286(18)	1973	25.6(9) s	β⁺ (25%)	²⁴⁹Fm	(7/2−)
^249m1Md^{[n 9]}	100(100)# keV			2001	1.5+1.2 −0.5 s [1.9(9) s]	α	²⁴⁵Es	(1/2−)
^249m2Md	≥910# keV			2021	2.8(5) ms			(19/2−)
²⁵⁰Md	101	149	250.084165(98)	1973	54(4) s	β⁺ (93.0%)	²⁵⁰Fm	2−#
						α (7.0%)	²⁴⁶Es
						β⁺, SF (0.026%)	(various)
^250mMd	120(40) keV			2019	42.4(45) s	α	²⁴⁶Es	7+#
²⁵¹Md	101	150	251.084774(20)	1973	4.21(23) min	β⁺ (90%)	²⁵¹Fm	(7/2−)
²⁵¹Md	101	150	251.084774(20)	1973	4.21(23) min	α (10%)	²⁴⁷Es	(7/2−)
^251mMd	53(8) keV			2021	20# s			(1/2−)
²⁵²Md	101	151	252.086385(98)	1973	2.3(8) min	β⁺	²⁵²Fm	1+#
²⁵³Md	101	152	253.087143(34)#	1992	6.4+11.6 −3.6 min [12(8) min]	β⁺ (~99.3%)	²⁵³Fm	(7/2−)
²⁵³Md	101	152	253.087143(34)#	1992	6.4+11.6 −3.6 min [12(8) min]	α (~0.7%)	²⁴⁹Es	(7/2−)
^253mMd	60(30) keV			(1971)^{[n 10]}	1# min			1/2−#
²⁵⁴Md	101	153	254.08959(11)#	1970	10(3) min	β⁺	²⁵⁴Fm	0−#
^254mMd^{[n 9]}	50(100)# keV			1970	28(8) min	β⁺	²⁵⁴Fm	3−#
²⁵⁵Md	101	154	255.0910817(60)	1958	27(2) min	β⁺ (93%)	²⁵⁵Fm	7/2−
²⁵⁵Md	101	154	255.0910817(60)	1958	27(2) min	α (7%)	²⁵¹Es	7/2−
²⁵⁶Md	101	155	256.09389(13)#	1955	77.7(18) min	β⁺ (90.8%)	²⁵⁶Fm	(1−)
						α (9.2%)	²⁵²Es
						SF (<3%)	(various)
²⁵⁷Md	101	156	257.0955373(17)	1965	5.52(5) h	EC (85%)	²⁵⁷Fm	(7/2−)
²⁵⁷Md	101	156	257.0955373(17)	1965	5.52(5) h	α (15%)	²⁵³Es	(7/2−)
²⁵⁸Md	101	157	258.0984336(37)	1970	51.59(29) d	α	²⁵⁴Es	8−#
						β⁻ (<0.0015%)	²⁵⁸No
						β⁺ (<0.0015%)	²⁵⁸Fm
^258mMd^{[n 9]}	0(200)# keV			1980	57.0(9) min	EC (85%)	²⁵⁸Fm	1−#
						SF (<15%)	(various)
						α (<1.2%)	²⁵⁴Es
²⁵⁹Md^{[n 11]}	101	158	259.10045(11)#	1982	1.60(6) h	SF	(various)	7/2−#
²⁶⁰Md	101	159	260.10365(34)#	1989	27.8(8) d	SF	(various)
						α (<5%)	²⁵⁶Es
						EC (<5%)	²⁶⁰Fm
						β⁻ (<3.5%)	²⁶⁰No
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[1]
^mMd – Excited nuclear isomer.
[2]
( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
[3]
# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
[4]
Modes of decay:

EC: Electron capture

SF: Spontaneous fission
[5]
( ) spin value – Indicates spin with weak assignment arguments.
[6]
# – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
[7]
Discovery of this isotope is disputed due to conflicting data.^[5]
[8]
Half-life only estimated, not included in discovery database
[9]
Order of ground state and isomer is uncertain.
[10]
Half-life not measured, not included in discovery database
[11]
Not directly synthesized, occurs as decay product of ²⁵⁹No

Chronology of isotope discovery

More information Isotope, Discovered ...

Isotope	Discovered	Reaction
²⁴⁴Md	2020	²⁰⁹Bi(⁴⁰Ar,5n)
²⁴⁵Md	1996	²⁰⁹Bi(⁴⁰Ar,4n)
²⁴⁶Md	1996	²⁰⁹Bi(⁴⁰Ar,3n)
²⁴⁷Md	1981	²⁰⁹Bi(⁴⁰Ar,2n)
²⁴⁸Md	1973	²⁴¹Am(¹²C,5n)
²⁴⁹Md	1973	²⁴¹Am(¹²C,4n)
²⁵⁰Md	1973	²⁴³Am(¹²C,5n), ²⁴³Am(¹³C,6n)
²⁵¹Md	1973	²⁴³Am(¹²C,4n), ²⁴³Am(¹³C,5n)
²⁵²Md	1973	²⁴³Am(¹³C,4n)
²⁵³Md	1992	²⁴³Am(¹³C,3n)
²⁵⁴Md	1970	²⁵³Es(α,3n)
²⁵⁵Md	1958	²⁵³Es(α,2n)
²⁵⁶Md	1955	²⁵³Es(α,n)
²⁵⁷Md	1964	²⁵²Cf(¹¹B,α2n)
²⁵⁸Md	1970	²⁵⁵Es(α,n)
²⁵⁹Md	1982	²⁴⁸Cm(¹⁸O,α3n)^[7]
²⁶⁰Md	1989	²⁵⁴Es+¹⁸O, ²²Ne — transfer

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Isotopes of mendelevium

List of isotopes

Chronology of isotope discovery

References

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