Mendelevium | Radioactive, Synthetic, Actinide

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data-icon="keyboard_arrow_right"></span> </button> </div> </div> <div class="mb-30 tlr-related-quizzes"> <div class="text-gray-900 p-5 font-serif font-14 font-weight-bold mx-10 mb-10"> Quizzes </div> <div class="imagelink-with-image-on-the-side card card-horizontal tlr-img-with-side-link ml-15 link-gray-900 mb-10" > <div class="position-relative card-media" style="flex: 0;"> <a class="ilf-image position-relative" href="/quiz/periodic-table-names-symbols-quiz"> <img loading="lazy" src="https://cdn.britannica.com/66/215466-131-16036BD8/Concept-artwork-periodic-table-elements.jpg?w=200&h=200&c=crop" alt="Concept artwork on the periodic table of elements." width="200" height="200" /> </a> </div> <div class="card-body ilf-content"> <a class="font-weight-semi-bold d-block mb-5 font-16 ilf-title" href="/quiz/periodic-table-names-symbols-quiz" >118 Names and Symbols of the Periodic Table Quiz</a> </div> </div> <div class="imagelink-with-image-on-the-side card card-horizontal 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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <a class="byline-edit-history" href="https://www.britannica.com/science/mendelevium/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/biography/Glenn-T-Seaborg" topicid="530808">Glenn T. Seaborg</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/chemical-element" topicid="108636">chemical element</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/mendelevium"> See all related content </a> </div> </div> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref625494"></span>mendelevium (Md)</strong>, <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="synthetic" href="https://www.merriam-webster.com/dictionary/synthetic" data-type="MW">synthetic</a> <a href="https://www.britannica.com/science/chemical-element" class="md-crosslink " data-show-preview="true">chemical element</a> of the <a href="https://www.britannica.com/science/actinoid-element" class="md-crosslink " data-show-preview="true">actinoid</a> series of the <a href="https://www.britannica.com/science/periodic-table" class="md-crosslink " data-show-preview="true">periodic table</a>, <a href="https://www.britannica.com/science/atomic-number" class="md-crosslink " data-show-preview="true">atomic number</a> 101. It was the first element to be synthesized and discovered a few <a href="https://www.britannica.com/science/atom" class="md-crosslink " data-show-preview="true">atoms</a> at a time. Not occurring in nature, mendelevium (as the <a href="https://www.britannica.com/science/isotope" class="md-crosslink " data-show-preview="true">isotope</a> mendelevium-256) was discovered (1955) by American chemists Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson, and <a href="https://www.britannica.com/biography/Glenn-T-Seaborg" class="md-crosslink " data-show-preview="true">Glenn T. Seaborg</a> at the <a href="https://www.britannica.com/topic/University-of-California" class="md-crosslink " data-show-preview="true">University of California</a>, Berkeley, as a product resulting from the <a href="https://www.britannica.com/science/helium-chemical-element" class="md-crosslink " data-show-preview="true">helium</a>-<a href="https://www.britannica.com/science/ion-physics" class="md-crosslink " data-show-preview="true">ion</a> (<a href="https://www.britannica.com/science/alpha-particle" class="md-crosslink " data-show-preview="true">alpha-particle</a>) bombardment of a minute quantity (about a billion atoms) of <a href="https://www.britannica.com/science/einsteinium" class="md-crosslink " data-show-preview="true">einsteinium</a>-253 (atomic number 99). The element was named after Russian chemist <a href="https://www.britannica.com/biography/Dmitri-Mendeleev" class="md-crosslink " data-show-preview="true">Dmitry Mendeleyev</a>.</p><div class="one-good-fact-module"> </div><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">In about a dozen repetitions of the experiment, the team of scientists produced 17 atoms of mendelevium, which were identified by the <a href="https://www.britannica.com/science/ion-exchange-reaction" class="md-crosslink " data-show-preview="true">ion-exchange</a> adsorption-elution method (mendelevium behaved like its <a href="https://www.britannica.com/science/rare-earth-element" class="md-crosslink " data-show-preview="true">rare-earth</a> homologue <a href="https://www.britannica.com/science/thulium" class="md-crosslink " data-show-preview="true">thulium</a>) and by the <a href="https://www.britannica.com/science/electron" class="md-crosslink " data-show-preview="true">electron</a>-capture <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="decay" href="https://www.britannica.com/dictionary/decay" data-type="EB">decay</a> of its daughter isotope <a href="https://www.britannica.com/science/fermium" class="md-crosslink " data-show-preview="true">fermium</a>-256. Fifteen other isotopes of mendelevium, all <a href="https://www.britannica.com/science/radioactivity" class="md-crosslink " data-show-preview="true">radioactive</a>, have been discovered. The stablest is mendelevium-258 (51.5-day <a href="https://www.britannica.com/science/half-life-radioactivity" class="md-crosslink " data-show-preview="true">half-life</a>). Studied by means of radioactive tracer techniques, mendelevium exhibits a predominant +3 <a href="https://www.britannica.com/science/oxidation-number" class="md-crosslink autoxref " data-show-preview="true">oxidation state</a>, as would be expected by its position in the actinoid series; a slightly stable +2 oxidation state is also known.</p><span class="marker MOD2 mod-inline"></span><div class="mb-20"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="299687" data-asm-type="infogram"><div class="md-assembly-wrapper card-media " data-type="infogram"><script id="infogram_0__/z8pqlTWwRHqAnaNwFRkn" src="https://e.infogram.com/js/dist/embed.js?Itp" type="text/javascript" title="Explore an interactive periodic table of the elements"></script></div></figure></div></div><div class="text-center pb-20"><div class="md-table-wrapper"><table class="md-element-table"><caption>Element Properties</caption><tbody><tr><th scope="row">atomic number</th><td>101</td></tr><tr><th scope="row">stablest isotope</th><td>258</td></tr><tr><th scope="row">oxidation states</th><td>+2, +3</td></tr><tr><th scope="row">electron configuration of gaseous atomic state</th><td>[Rn]5<em>f</em><sup> </sup><sup>1</sup><sup>3</sup>7<em>s</em><sup>2</sup></td></tr></tbody></table></div></div></section> <span class="md-signature"><a href="/contributor/Lester-Morss/9300153">Lester Morss</a></span> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":1,"pageId":374759,"pageLength":205,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"A","adLeg":"A","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"SMALL","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Mendelevium | Radioactive, Synthetic, Actinide | Britannica