Mendelevium (Md)
actinideSolid
मानक परमाणु भार
[258]इलेक्ट्रॉन विन्यास
[Rn] 7s2 5f13गलनांक
826.85 °Cक्वथनांक
उपलब्ध नहींघनत्व
1.03e+4 kg/m³ऑक्सीकरण अवस्थाएँ
+2, +3विद्युतऋणात्मकता (पॉलिंग)
1.3आयनन ऊर्जा (प्रथम)
6.58 eVखोज का वर्ष
1955परमाणु त्रिज्या
उपलब्ध नहींविवरण
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.
चित्र
गुण
भौतिक
- वान डर वाल्स त्रिज्या
- 246 pm सभी तत्वों की वान डर वाल्स त्रिज्या की तुलना करें →
- घनत्व
- 1.03 × 104 kg/m³ सभी तत्वों की घनत्व की तुलना करें →
- STP पर प्रावस्था
- ठोस सभी तत्वों की STP पर प्रावस्था की तुलना करें →
- गलनांक
- 826.85 °C सभी तत्वों की गलनांक की तुलना करें →
रासायनिक
- विद्युतऋणात्मकता (पॉलिंग)
- 1.3 सभी तत्वों की विद्युतऋणात्मकता (पॉलिंग) की तुलना करें →
- इलेक्ट्रॉन बंधुता
- 0.997 eV
- आयनन ऊर्जा (प्रथम)
- 6.58 eV सभी तत्वों की आयनन ऊर्जा (प्रथम) की तुलना करें →
- आयनन ऊर्जा (द्वितीय)
- 12.400043 eV सभी तत्वों की आयनन ऊर्जा (द्वितीय) की तुलना करें →
- आयनन ऊर्जा (तृतीय)
- 24.300084 eV सभी तत्वों की आयनन ऊर्जा (तृतीय) की तुलना करें →
- आयनन ऊर्जा (चतुर्थ)
- 40.000138 eV सभी तत्वों की आयनन ऊर्जा (चतुर्थ) की तुलना करें →
- आयनन ऊर्जा (पंचम)
- 54.100186 eV सभी तत्वों की आयनन ऊर्जा (पंचम) की तुलना करें →
- ऑक्सीकरण अवस्थाएँ
- +2, +3 सभी तत्वों की ऑक्सीकरण अवस्थाएँ की तुलना करें →
- संयोजकता इलेक्ट्रॉन
- 3 सभी तत्वों की संयोजकता इलेक्ट्रॉन की तुलना करें →
- इलेक्ट्रॉन विन्यास
- [Rn] 7s2 5f13
ऊष्मागतिक
- ऊर्ध्वपातन ऊष्मा
- 4.197544 eV
- परमाणुकरण ऊष्मा
- 4.197544 eV
नाभिकीय
- प्रोटॉन
- 101 सभी तत्वों की प्रोटॉन की तुलना करें →
- न्यूट्रॉन
- 157 सभी तत्वों की न्यूट्रॉन की तुलना करें →
- ज्ञात समस्थानिक
- 19 सभी तत्वों की ज्ञात समस्थानिक की तुलना करें →
- स्थिर समस्थानिक
- 0 सभी तत्वों की स्थिर समस्थानिक की तुलना करें →
- द्रव्यमान संख्या (सबसे स्थिर)
- 258
- सबसे स्थिर समस्थानिक
- Md-258
- खोज का वर्ष
- 1955
प्रचुरता
उपलब्ध नहीं
क्रिस्टल संरचना
उपलब्ध नहीं
इलेक्ट्रॉनिक संरचना
- प्रति कोश इलेक्ट्रॉन
- 2, 8, 18, 32, 31, 8, 2 सभी तत्वों की प्रति कोश इलेक्ट्रॉन की तुलना करें →
पहचानकर्ता
- CAS संख्या
- 7440-11-1 सभी तत्वों की CAS संख्या की तुलना करें →
- टर्म प्रतीक
- 2F°7/2
- InChI
- InChI=1S/Md
- InChI कुंजी
- MQVSLOYRCXQRPM-UHFFFAOYSA-N
इलेक्ट्रॉन विन्यास मापित
Md: 5f¹³ 7s²[Rn] 5f¹³ 7s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁶ 5f¹³ 7s²परमाणु मॉडल
समस्थानिक न्यूट्रॉन की संख्या, द्रव्यमान और स्थिरता बदलते हैं — उदासीन परमाणु का इलेक्ट्रॉन विन्यास नहीं।
सांकेतिक परमाणु मॉडल, वास्तविक अनुपात में नहीं।
परमाणु पहचान-चिह्न
उत्सर्जन / अवशोषण स्पेक्ट्रम
समस्थानिक वितरण
कोई स्थिर समस्थानिक नहीं है।
| द्रव्यमान संख्या | परमाणु द्रव्यमान (u) | प्राकृतिक प्रचुरता | अर्धायु |
|---|---|---|---|
| 256 रेडियोधर्मी | 256.09389 ± 0.00013 | उपलब्ध नहीं | 77.7 मिनट |
| 250 रेडियोधर्मी | 250.08441 ± 0.00032 | उपलब्ध नहीं | 54 सेकंड |
| 258 रेडियोधर्मी | 258.0984315 ± 0.000005 | उपलब्ध नहीं | 51.59 दिन |
| 261 रेडियोधर्मी | 261.10583 ± 0.00062 | उपलब्ध नहीं | 40 मिनट |
| 260 रेडियोधर्मी | 260.10365 ± 0.00034 | उपलब्ध नहीं | 27.8 दिन |
प्रावस्था / अवस्था
कारण: ऊर्ध्वपातनांक (826.85 °C) से 801.9 °C कम
सांकेतिक, वास्तविक अनुपात में नहीं
प्रावस्था संक्रमण बिंदु
संक्रमण ऊर्जाएँ
ऊर्ध्वपातनांक पर 1 mol के ऊर्ध्वपातन के लिए आवश्यक ऊर्जा
घनत्व
मानक परिस्थितियों में
मानक परिस्थितियों में
परमाणु स्पेक्ट्रम
101 में से 10 दिखाए जा रहे हैं। आयन के आवेश के अनुसार आरोही क्रम में व्यवस्थित।
उपलब्ध ऊर्जा स्तर डेटा ?
| आयन | आवेश | स्तर |
|---|---|---|
| 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 |
क्रिस्टल संरचना का डेटा उपलब्ध नहीं है
आयनिक त्रिज्याएँ
| आवेश | उपसहसंयोजन | प्रचक्रण | त्रिज्या |
|---|---|---|---|
| +3 | 9 | उपलब्ध नहीं | 109.5 pm |
यौगिक
समस्थानिक (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.
| द्रव्यमान संख्या | परमाणु द्रव्यमान (u) | प्राकृतिक प्रचुरता | अर्धायु | क्षय का प्रकार | |
|---|---|---|---|---|---|
| 256 रेडियोधर्मी | 256.09389 ± 0.00013 | उपलब्ध नहीं | 77.7 मिनट | β+ =90.8±0.7%α =9.2±0.7%SF<3% | |
| 250 रेडियोधर्मी | 250.08441 ± 0.00032 | उपलब्ध नहीं | 54 सेकंड | β+ =93.0±0.8%α =7.0±0.8%β+SF =0.026±1.5% | |
| 258 रेडियोधर्मी | 258.0984315 ± 0.000005 | उपलब्ध नहीं | 51.59 दिन | α ≈100%β+<0.0015% β-<0.0015% | |
| 261 रेडियोधर्मी | 261.10583 ± 0.00062 | उपलब्ध नहीं | 40 मिनट | α ? | |
| 260 रेडियोधर्मी | 260.10365 ± 0.00034 | उपलब्ध नहीं | 27.8 दिन | SF ≈100%α<5% ε<5% |
विस्तृत गुण
सहसंयोजक त्रिज्याएँ (विस्तृत)
- सहसंयोजक त्रिज्या (प्यूक्को)
- 173 pm
- सहसंयोजक त्रिज्या (प्यूक्को, द्विबंध)
- 139 pm
वान डर वाल्स त्रिज्याएँ
- UFF
- 327.4 pm
संख्यांकन मापक्रम
- Mendeleev
- 38
- Pettifor
- 36
- Glawe
- 45
विद्युतऋणात्मकता मापक्रम
- Ghosh
- 0
ध्रुवणीयता और परिक्षेपण
- द्विध्रुव ध्रुवणीयता
- 109 a.u.
- द्विध्रुव ध्रुवणीयता (अनिश्चितता)
- 20 a.u.
प्रावस्था संक्रमण और अपररूप
| गलनांक | 1100.15 K |
ऑक्सीकरण अवस्था की श्रेणियाँ
उन्नत संदर्भ डेटा
क्रिस्टल त्रिज्याओं का विवरण (1)
| आवेश | CN | प्रचक्रण | rcrystal (pm) | उत्पत्ति |
|---|---|---|---|---|
| 3 | IX | — | 123.5 |
समस्थानिक क्षय के प्रकार (45)
| समस्थानिक | मोड | तीव्रता |
|---|---|---|
| 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% |
अतिरिक्त डेटा
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
Not Applicable
संदर्भ (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
Not Applicable
संदर्भ (1)
- [5] Mendelevium https://education.jlab.org/itselemental/ele101.html
संदर्भ
(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.