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.

List of isotopes

|-id=Mendelevium-244 | rowspan=2|²⁴⁴Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 143 | rowspan=2|244.08116(40)# | rowspan=2|<br>[] | α | ²⁴⁰Es | rowspan=2|3+# |- | β⁺, SF (<14%) | (various) |-id=Mendelevium-244m | style="text-indent:1em" | ^244mMd | colspan="3" style="text-indent:2em" | 200(150)#&nbsp;keV | ~9&nbsp;μs | IT | ²⁴⁴Md | 7+# |-id=Mendelevium-245 | ²⁴⁵Md | style="text-align:right" | 101 | style="text-align:right" | 144 | 245.08086(28)# | 0.38(10)&nbsp;s | α | ²⁴¹Es | (7/2−) |-id=Mendelevium-245m | style="text-indent:1em" | ^245mMd | colspan="3" style="text-indent:2em" | 100(100)#&nbsp;keV | 0.90(25)&nbsp;ms | SF | (various) | 1/2−# |-id=Mendelevium-246 | ²⁴⁶Md | style="text-align:right" | 101 | style="text-align:right" | 145 | 246.08171(28)# | 0.92(18)&nbsp;s | α | ²⁴²Es | 1−# |-id=Mendelevium-246m | rowspan=3 style="text-indent:1em" | ^246mMd | rowspan=3 colspan="3" style="text-indent:2em" | 60(60)&nbsp;keV | rowspan=3| | β⁺ (~67%) | ²⁴⁶Fm | rowspan=3|4−# |- | α (<23%) | ²⁴²Es |- | β⁺, SF (>10%) | (various) |-id=Mendelevium-247 | rowspan=2|²⁴⁷Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 146 | rowspan=2|247.08152(22)# | rowspan=2| | α (99.14%) | ²⁴³Es | rowspan=2|(7/2−) |- | SF (0.86%) | (various) |-id=Mendelevium-247m | rowspan=2 style="text-indent:1em" | ^247mMd | rowspan=2 colspan="3" style="text-indent:2em" | 153&nbsp;keV | rowspan=2| | α (80%) | ²⁴³Es | rowspan=2|(1/2−) |- | SF (20%) | (various) |-id=Mendelevium-248 | rowspan=3|²⁴⁸Md | rowspan=3 style="text-align:right" | 101 | rowspan=3 style="text-align:right" | 147 | rowspan=3|248.08261(20)# | rowspan=3| | β⁺ (80%) | ²⁴⁸Fm | rowspan=3| |- | α (20%) | ²⁴⁴Es |- | β⁺, SF (<0.05%) | (various) |-id=Mendelevium-249 | rowspan=2|²⁴⁹Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 148 | rowspan=2|249.08286(18) | rowspan=2| | α (75%) | ²⁴⁵Es | rowspan=2|(7/2−) |- | β⁺ (25%) | ²⁴⁹Fm |-id=Mendelevium-249m | style="text-indent:1em" | ^249mMd | colspan="3" style="text-indent:2em" | 100(100)#&nbsp;keV | <br>[] | α | ²⁴⁵Es | (1/2−) |-id=Mendelevium-250 | rowspan=3|²⁵⁰Md | rowspan=3 style="text-align:right" | 101 | rowspan=3 style="text-align:right" | 149 | rowspan=3|250.084165(98) | rowspan=3|54(4)&nbsp;s | β⁺ (93.0%) | ²⁵⁰Fm | rowspan=3|2−# |- | α (7.0%) | ²⁴⁶Es |- | β⁺, SF (0.026%) | (various) |-id=Mendelevium-250m | style="text-indent:1em" | ^250mMd | colspan="3" style="text-indent:2em" | 120(40)&nbsp;keV | 42.4(45)&nbsp;s | α | ²⁴⁶Es | 7+# |-id=Mendelevium-251 | rowspan=2|²⁵¹Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 150 | rowspan=2|251.084774(20) | rowspan=2| | β⁺ (90%) | ²⁵¹Fm | rowspan=2|(7/2−) |- | α (10%) | ²⁴⁷Es |-id=Mendelevium-251m | style="text-indent:1em" | ^251mMd | colspan="3" style="text-indent:2em" | 53(8)&nbsp;keV | 20#&nbsp;s | | | (1/2−) |-id=Mendelevium-252 | ²⁵²Md | style="text-align:right" | 101 | style="text-align:right" | 151 | 252.086385(98) | | β⁺ | ²⁵²Fm | 1+# |- | rowspan=2|²⁵³Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 152 | rowspan=2|253.087143(34)# | rowspan=2|<br>[] | β⁺ (~99.3%) | ²⁵³Fm | rowspan=2|(7/2−) |- | α (~0.7%) | ²⁴⁹Es |-id=Mendelevium-253m | style="text-indent:1em" | ^253mMd | colspan="3" style="text-indent:2em" | 60(30)&nbsp;keV | 1#&nbsp;min | | | 1/2−# |-id=Mendelevium-254 | ²⁵⁴Md | style="text-align:right" | 101 | style="text-align:right" | 153 | 254.08959(11)# | | β⁺ | ²⁵⁴Fm | 0−# |-id=Mendelevium-254m | style="text-indent:1em" | ^254mMd | colspan="3" style="text-indent:2em" | 50(100)#&nbsp;keV | | β⁺ | ²⁵⁴Fm | 3−# |-id=Mendelevium-255 | rowspan=2|²⁵⁵Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 154 | rowspan=2|255.0910817(60) | rowspan=2| | β⁺ (93%) | ²⁵⁵Fm | rowspan=2|7/2− |- | α (7%) | ²⁵¹Es |-id=Mendelevium-256 | rowspan=3|²⁵⁶Md | rowspan=3 style="text-align:right" | 101 | rowspan=3 style="text-align:right" | 155 | rowspan=3|256.09389(13)# | rowspan=3| | β⁺ (90.8%) | ²⁵⁶Fm | rowspan=3|(1−) |- | α (9.2%) | ²⁵²Es |- | SF (<3%) | (various) |-id=Mendelevium-257 | rowspan=2|²⁵⁷Md | rowspan=2 style="text-align:right" | 101 | rowspan=2 style="text-align:right" | 156 | rowspan=2|257.0955373(17) | rowspan=2| | EC (85%) | ²⁵⁷Fm | rowspan=2|(7/2−) |- | α (15%) | ²⁵³Es |-id=Mendelevium-258 | rowspan=3|²⁵⁸Md | rowspan=3 style="text-align:right" | 101 | rowspan=3 style="text-align:right" | 157 | rowspan=3|258.0984336(37) | rowspan=3| | α | ²⁵⁴Es | rowspan=3|8−# |- | β^− (<0.0015%) | ²⁵⁸No |- | β⁺ (<0.0015%) | ²⁵⁸Fm |-id=Mendelevium-258m | rowspan=3 style="text-indent:1em" | ^258mMd | rowspan=3 colspan="3" style="text-indent:2em" | 0(200)#&nbsp;keV | rowspan=3| | EC (85%) | ²⁵⁸Fm | rowspan=3|1−# |- | SF (<15%) | (various) |- | α (<1.2%) | ²⁵⁴Es |-id=Mendelevium-259 | ²⁵⁹Md | style="text-align:right" | 101 | style="text-align:right" | 158 | 259.10045(11)# | | SF | (various) | 7/2−# |- | rowspan=4|²⁶⁰Md | rowspan=4 style="text-align:right" | 101 | rowspan=4 style="text-align:right" | 159 | rowspan=4|260.10365(34)# | rowspan=4| | SF | (various) | rowspan=4| |- | α (<5%) | ²⁵⁶Es |- | EC (<5%) | ²⁶⁰Fm |- | β^− (<3.5%) | ²⁶⁰No

Chronology of isotope discovery

References

• Isotope masses from:
• Half-life, spin, and isomer data selected from the following sources.