Mendelevium (Md)
actinideSolid
Masse atomique relative standard
[258]Configuration électronique
[Rn] 7s2 5f13Point de fusion
826,85 °CPoint d’ébullition
N/DMasse volumique
1,03e+4 kg/m³États d’oxydation
+2, +3Électronégativité (Pauling)
1,3Énergie d’ionisation (1re)
6,58 eVAnnée de découverte
1955Rayon atomique
N/DDétails
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.
Images
Propriétés
Propriétés physiques
- Rayon de van der Waals
- 246 pm Comparer : Rayon de van der Waals de tous les éléments →
- Masse volumique
- 1,03 × 104 kg/m³ Comparer : Masse volumique de tous les éléments →
- Phase aux CNTP
- Solide Comparer : Phase aux CNTP de tous les éléments →
- Point de fusion
- 826,85 °C Comparer : Point de fusion de tous les éléments →
Propriétés chimiques
- Électronégativité (Pauling)
- 1,3 Comparer : Électronégativité (Pauling) de tous les éléments →
- Affinité électronique
- 0,997 eV
- Énergie d’ionisation (1re)
- 6,58 eV Comparer : Énergie d’ionisation (1re) de tous les éléments →
- Énergie d’ionisation (2e)
- 12,400043 eV Comparer : Énergie d’ionisation (2e) de tous les éléments →
- Énergie d’ionisation (3e)
- 24,300084 eV Comparer : Énergie d’ionisation (3e) de tous les éléments →
- Énergie d’ionisation (4e)
- 40,000138 eV Comparer : Énergie d’ionisation (4e) de tous les éléments →
- Énergie d’ionisation (5e)
- 54,100186 eV Comparer : Énergie d’ionisation (5e) de tous les éléments →
- États d’oxydation
- +2, +3 Comparer : États d’oxydation de tous les éléments →
- Électrons de valence
- 3 Comparer : Électrons de valence de tous les éléments →
- Configuration électronique
- [Rn] 7s2 5f13
Propriétés thermodynamiques
- Enthalpie de sublimation
- 4,197544 eV
- Enthalpie d’atomisation
- 4,197544 eV
Propriétés nucléaires
- Protons
- 101 Comparer : Protons de tous les éléments →
- Neutrons
- 157 Comparer : Neutrons de tous les éléments →
- Isotopes connus
- 19 Comparer : Isotopes connus de tous les éléments →
- Isotopes stables
- 0 Comparer : Isotopes stables de tous les éléments →
- Nombre de masse (isotope le plus stable)
- 258
- Isotope le plus stable
- Md-258
- Année de découverte
- 1955
Abondance
N/D
Structure cristalline
N/D
Structure électronique
- Électrons par couche
- 2, 8, 18, 32, 31, 8, 2 Comparer : Électrons par couche de tous les éléments →
Identifiants
- Numéro CAS
- 7440-11-1 Comparer : Numéro CAS de tous les éléments →
- Symbole de terme
- 2F°7/2
- InChI
- InChI=1S/Md
- Clé InChI
- MQVSLOYRCXQRPM-UHFFFAOYSA-N
Configuration électronique Mesuré
Md: 5f¹³ 7s²[Rn] 5f¹³ 7s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹³ 7s²Modèle atomique
Les isotopes diffèrent par leur nombre de neutrons, leur masse et leur stabilité — pas par la configuration électronique de l’atome neutre.
Modèle atomique schématique, non à l’échelle.
Empreinte atomique
Spectre d’émission / d’absorption
Distribution isotopique
Aucun isotope stable.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie |
|---|---|---|---|
| 256 Radioactif | 256,09389 ± 0,00013 | N/D | 77.7 minutes |
| 250 Radioactif | 250,08441 ± 0,00032 | N/D | 54 secondes |
| 258 Radioactif | 258,0984315 ± 0,000005 | N/D | 51.59 jours |
| 261 Radioactif | 261,10583 ± 0,00062 | N/D | 40 minutes |
| 260 Radioactif | 260,10365 ± 0,00034 | N/D | 27.8 jours |
Phase / État
Explication: 801,9 °C en dessous du point de sublimation (826,85 °C)
Schématique, non à l’échelle
Points de transition de phase
Énergies de transition
Énergie nécessaire pour sublimer 1 mol au point de sublimation
Masse volumique
Dans les conditions standard
Dans les conditions standard
Spectres atomiques
Affichage de 10 sur 101. Tri par charge ionique croissante.
Niveaux répertoriés ?
| Ion | Charge | Niveaux |
|---|---|---|
| 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 |
Données de structure cristalline indisponibles
Rayons ioniques
| Charge | Coordinence | Spin | Rayon |
|---|---|---|---|
| +3 | 9 | N/D | 109.5 pm |
Composés
Isotopes (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.
| Nombre de masse | Masse atomique (u) | Abondance naturelle | Demi-vie | Mode de désintégration | |
|---|---|---|---|---|---|
| 256 Radioactif | 256,09389 ± 0,00013 | N/D | 77.7 minutes | β+ =90.8±0.7%α =9.2±0.7%SF<3% | |
| 250 Radioactif | 250,08441 ± 0,00032 | N/D | 54 secondes | β+ =93.0±0.8%α =7.0±0.8%β+SF =0.026±1.5% | |
| 258 Radioactif | 258,0984315 ± 0,000005 | N/D | 51.59 jours | α ≈100%β+<0.0015% β-<0.0015% | |
| 261 Radioactif | 261,10583 ± 0,00062 | N/D | 40 minutes | α ? | |
| 260 Radioactif | 260,10365 ± 0,00034 | N/D | 27.8 jours | SF ≈100%α<5% ε<5% |
Propriétés étendues
Rayons covalents (données étendues)
- Rayon covalent (Pyykkö)
- 173 pm
- Rayon covalent (Pyykkö, liaison double)
- 139 pm
Rayons de van der Waals
- UFF
- 327,4 pm
Échelles de numérotation
- Mendeleev
- 38
- Pettifor
- 36
- Glawe
- 45
Échelles d’électronégativité
- Ghosh
- 0
Polarisabilité et dispersion
- Polarisabilité dipolaire
- 109 a.u.
- Polarisabilité dipolaire (incertitude)
- 20 a.u.
Transitions de phase et allotropes
| Point de fusion | 1100,15 K |
Catégories d’états d’oxydation
Données de référence avancées
Détail des rayons cristallins (1)
| Charge | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 3 | IX | — | 123,5 |
Modes de désintégration des isotopes (45)
| Isotope | Mode | Intensité |
|---|---|---|
| 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% |
Données complémentaires
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
Références (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
Références (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
Références
(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.