Mendelevium (Md)
actinideSolid
标准原子量
[258]电子排布
[Rn] 7s2 5f13熔点
826.85 °C沸点
暂无密度
1.03e+4 kg/m³氧化态
+2, +3电负性（鲍林）
1.3第一电离能
6.58 eV发现年份
1955原子半径
暂无详细信息
Mendelevium is a synthetic actinide and the first element that was initially identified one atom at a time. All known isotopes are radioactive, and none is present in nature in measurable primordial amounts. Its chemistry is dominated by the +3 oxidation state, broadly resembling neighboring late actinides and lanthanides, with a distinctive accessible +2 state under reducing conditions. Work on mendelevium is limited by very small samples and short half-lives.
Mendelevium does not occur naturally in the Earth’s crust. It was first synthesized in 1955 by Glenn T. Seaborg and his team at the University of California using the reactions 253Es (4He, n) 256Md and 253Es (4He, 2n) 255Md. Mendelevium is named for the Russian scientist, Dmitri Mendeleev (Fig. IUPAC.101.1), who developed the Periodic Table of the chemical elements [636], [637]. There are no applications for isotopes of mendelevium aside from scientific research.
Experiments seem to show that the element possesses a moderately stable dipositive (II) oxidation state in addition to the tripositive (III) oxidation state, which is characteristic of the actinide elements.
Mendelevium was first produced by Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin and Albert Ghiorso working at the University of California, Berkeley, in 1955. They bombarded atoms of einsteinium-253 with helium ions using a device known as a cyclotron. This produced atoms of mendelevium-256, an isotope with a half-life of about 77 minutes, and a free neutron. Mendelevium's most stable isotope, mendelevium-258, has a half-life of about 51.5 days. It decays into einsteinium-254 through alpha decay or decays through spontaneous fission.
Mendelevium is named after Dmitri Mendeleev. It is the ninth transuranium element of the actinide series discovered. It was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope 253Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was 256Md, which has a half-life of 76 min. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis.
No macroscopic sample of mendelevium has been isolated, so its real bulk appearance is unknown. A metallic solid is expected by periodic trends, but color, texture, density, and other ordinary bulk properties have not been directly measured.
Mendelevium has no practical use outside scientific research. Its isotopes are produced for nuclear-chemistry studies, tracer-scale separation experiments, and investigations of actinide electronic structure and redox behavior. Historically, mendelevium was important in demonstrating that new elements could be discovered and chemically characterized from only a few atoms. It is not used in medicine, industry, consumer products, or power generation.
Since only small amounts of mendelevium have ever been produced, it currently has no uses outside of basic scientific research.
256Md has been used to elucidate some of the chemical properties of mendelevium in aqueous solution.
Mendelevium chemistry has been studied in solution and on surfaces at tracer scale. The Md³⁺ ion is the most stable aqueous form and behaves much like a heavy trivalent actinide. The Md²⁺ ion can be produced by reduction and is unusually important for identifying mendelevium relative to many neighboring actinides. Simple compounds such as mendelevium(III) chloride, MdCl₃, and mendelevium(III) fluoride, MdF₃, are inferred or studied only in minute quantities; no bulk compound chemistry exists.
See more information at the Mendelevium compound page.
The main hazard from mendelevium is ionizing radiation, with risk depending strongly on isotope, activity, chemical form, and containment. The longest-lived isotope, ²⁵⁸Md, has a half-life of about 51 days, while many others decay much faster. Amounts normally handled are extremely small, but work requires specialized radiochemical facilities to prevent contamination and external or internal exposure.
Mendelevium has no significant natural environmental cycle. Any environmental presence would come from specialized nuclear research or decay chains in artificial material and would involve vanishingly small quantities. Because it is radioactive and produced atom by atom or in tracer amounts, its environmental chemistry is inferred mainly from actinide behavior rather than observed field distribution.
Mendelevium is not a traded commodity and has no commercial supply chain. It is made in high-flux reactors or particle accelerators by neutron capture and charged-particle nuclear reactions involving heavy actinide targets, followed by rapid radiochemical separation. Production yields are extremely small, often atom-scale to tracer-scale, and are constrained by target availability, irradiation time, isotope half-life, and the need for specialized laboratories. There is no meaningful recycling market or industrial substitution issue because demand is confined to research.
Made by bombarding einsteinium with helium ions.
Mendelevium is not expected to have appreciable cosmic abundance. Its isotopes have half-lives far too short to survive since stellar nucleosynthesis or Solar System formation. It may be formed transiently in extreme neutron-rich events or in artificial nuclear reactions, but any naturally produced atoms would decay quickly and would not accumulate in planets, meteorites, or interstellar matter.
- Mendelevium was named for Dmitri Mendeleev, the developer of the periodic table.
- The first identification used only about a few atoms produced by bombarding einsteinium.
- Its accessible +2 state is a key diagnostic feature in radiochemical separations.
- ²⁵⁶Md has been used in atom-at-a-time chemical studies despite its short half-life.
- No weighing, casting, or visual inspection of elemental mendelevium has been possible.
图片
性质
物理性质
- 范德华半径
- 246 pm 比较所有元素的范德华半径 →
- 密度
- 1.03 × 104 kg/m³ 比较所有元素的密度 →
- 标准温度和压力下的物相
- 固态 比较所有元素的标准温度和压力下的物相 →
- 熔点
- 826.85 °C 比较所有元素的熔点 →
化学性质
- 电负性（鲍林）
- 1.3 比较所有元素的电负性（鲍林） →
- 电子亲和能
- 0.997 eV
- 第一电离能
- 6.58 eV 比较所有元素的第一电离能 →
- 第二电离能
- 12.400043 eV 比较所有元素的第二电离能 →
- 第三电离能
- 24.300084 eV 比较所有元素的第三电离能 →
- 第四电离能
- 40.000138 eV 比较所有元素的第四电离能 →
- 第五电离能
- 54.100186 eV 比较所有元素的第五电离能 →
- 氧化态
- +2, +3 比较所有元素的氧化态 →
- 价电子
- 3 比较所有元素的价电子 →
- 电子排布
- [Rn] 7s2 5f13
热力学性质
- 升华热
- 4.197544 eV
- 原子化热
- 4.197544 eV
核性质
- 质子
- 101 比较所有元素的质子 →
- 中子
- 157 比较所有元素的中子 →
- 已知同位素
- 19 比较所有元素的已知同位素 →
- 稳定同位素
- 0 比较所有元素的稳定同位素 →
- 质量数（最稳定同位素）
- 258
- 最稳定同位素
- Md-258
- 发现年份
- 1955
丰度
暂无
晶体结构
暂无
电子结构
- 各电子层电子数
- 2, 8, 18, 32, 31, 8, 2 比较所有元素的各电子层电子数 →
标识符
- CAS登记号
- 7440-11-1 比较所有元素的CAS登记号 →
- 谱项符号
- 2F°7/2
- InChI
- InChI=1S/Md
- InChI Key
- MQVSLOYRCXQRPM-UHFFFAOYSA-N
电子排布 实测值
Md: 5f¹³ 7s²[Rn] 5f¹³ 7s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹³ 7s²原子模型
不同同位素的中子数、质量和稳定性不同，但中性原子的电子排布不变。
原子模型示意图，未按比例绘制。
原子指纹
发射 / 吸收光谱
同位素分布
无稳定同位素。
| 质量数 | 原子质量（u） | 天然丰度 | 半衰期 |
|---|---|---|---|
| 256 放射性 | 256.09389 ± 0.00013 | 暂无 | 77.7 分钟 |
| 250 放射性 | 250.08441 ± 0.00032 | 暂无 | 54 秒 |
| 258 放射性 | 258.0984315 ± 0.000005 | 暂无 | 51.59 天 |
| 261 放射性 | 261.10583 ± 0.00062 | 暂无 | 40 分钟 |
| 260 放射性 | 260.10365 ± 0.00034 | 暂无 | 27.8 天 |
物相 / 状态
原因: 低于升华点（826.85 °C）801.9 °C
示意图，未按比例绘制
相变点
相变能
在升华点升华1 mol物质所需的能量
密度
标准条件下
标准条件下
原子光谱
已显示10项，共101项。 按离子电荷升序排列。
收录能级 ?
| 离子 | 电荷 | 能级 |
|---|---|---|
| Md I | 0 | 2 |
| Md II | +1 | 2 |
| Md III | +2 | 2 |
| Md IV | +3 | 2 |
| Md V | +4 | 2 |
| Md VI | +5 | 2 |
| Md VII | +6 | 2 |
| Md VIII | +7 | 2 |
| Md IX | +8 | 2 |
| Md X | +9 | 2 |
暂无晶体结构数据
离子半径
| 电荷 | 配位 | 自旋 | 半径 |
|---|---|---|---|
| +3 | 9 | 暂无 | 109.5 pm |
化合物
同位素 (5)
Fourteen isotopes are now recognized. 258Md has a half-life of 2 months. This isotope has been produced by the bombardment of an isotope of einsteinium with ions of helium. Eventually enough 258Md should be made to determine its physical properties.
| 质量数 | 原子质量（u） | 天然丰度 | 半衰期 | 衰变方式 | |
|---|---|---|---|---|---|
| 256 放射性 | 256.09389 ± 0.00013 | 暂无 | 77.7 分钟 | β+ =90.8±0.7%α =9.2±0.7%SF<3% | |
| 250 放射性 | 250.08441 ± 0.00032 | 暂无 | 54 秒 | β+ =93.0±0.8%α =7.0±0.8%β+SF =0.026±1.5% | |
| 258 放射性 | 258.0984315 ± 0.000005 | 暂无 | 51.59 天 | α ≈100%β+<0.0015% β-<0.0015% | |
| 261 放射性 | 261.10583 ± 0.00062 | 暂无 | 40 分钟 | α ? | |
| 260 放射性 | 260.10365 ± 0.00034 | 暂无 | 27.8 天 | SF ≈100%α<5% ε<5% |
扩展性质
共价半径（扩展）
- 共价半径（Pyykkö）
- 173 pm
- 共价半径（Pyykkö，双键）
- 139 pm
范德华半径
- UFF
- 327.4 pm
编号标度
- Mendeleev
- 38
- Pettifor
- 36
- Glawe
- 45
电负性标度
- Ghosh
- 0
极化率与色散
- 偶极极化率
- 109 a.u.
- 偶极极化率（不确定度）
- 20 a.u.
相变与同素异形体
| 熔点 | 1100.15 K |
氧化态分类
高级参考数据
晶体半径详情 (1)
| 电荷 | CN | 自旋 | rcrystal (pm) | 来源 |
|---|---|---|---|---|
| 3 | IX | — | 123.5 |
同位素衰变方式 (45)
| 同位素 | 模式 | 强度 |
|---|---|---|
| 244 | A | 100% |
| 244 | B+ | — |
| 244 | B+SF | 14% |
| 245 | A | 100% |
| 245 | B+ | — |
| 246 | A | 100% |
| 247 | A | 100% |
| 247 | SF | 0.1% |
| 248 | B+ | 80% |
| 248 | A | 20% |
补充数据
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
参考文献 (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
参考文献 (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
参考文献
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Mendelevium.
The element property data was retrieved from publications.