radium - LAROUSSE

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href="/dictionnaires/francais/radium/66150">radium</a></aside> <p class="definition">Métal alcalino-terreux radioactif. (Élément chimique de symbole Ra.)</p> <p class="blanc-avant">Découvert dans la pechblende en 1898 par P. et M. Curie, puis préparé sous forme métallique en 1910, le radium fond à 700 °C et décompose l'eau à froid. On connaît 25 isotopes, tous radioactifs, dont les nombres de masse sont compris entre 206 et 230 et dont le numéro atomique est 88. L'isotope 226 est radioactif α (période 1 622 ans) et donne naissance à un gaz radioactif : le radon 222. L'isotope 228 est radioactif β<sup>−</sup> (période 6,7 ans). Ces deux isotopes sont les plus abondants ; on les trouve respectivement dans les minerais d'uranium et de thorium, dont ils sont extraits. Les effets biologiques du radium proviennent des rayonnements émis par lui-même ou par ses produits de filiation. Dans l'organisme, il se fixe principalement sur la moelle osseuse et sur le squelette. Il a été longtemps le seul radio-isotope utilisé en gammagraphie et en curiethérapie.</p> </article> <div class="panel-pays"> </div> <div class="rwm-podcast-player" data-pid="1eca0639-3a13-635a-a5fc-c9380f86a94d"></div> </div> <div class="col-md-4"> <div class="pub-pave oasm"> </div> <div class="panel-da"> <div class="banner-title"> <hr class="line-left" /><span class="fontello"></span> <hr class="line-right" /> <p class="panel-title">Articles associés</p> </div> <div class="zone-articles"> <article><a href="/encyclopedie/divers/atome/23753"> <h2><B>atome.</B></h2> <p>Constituant fondamental de la matière dont les mouvements et les combinaisons rendent compte de l'essentiel des propriétés macroscopiques de celle-ci...</p></a> </article> <article><a href="/encyclopedie/divers/%C3%A9l%C3%A9ment/46349"> <h2><B>élément.</B></h2> <p>Entité chimique fondamentale commune aux diverses variétés d'un même corps simple ainsi qu'aux combinaisons de ce corps simple avec d'autres corps...</p></a> </article> </div> <div class="banner-title"> <hr class="line-left" /><span class="fontello"></span> <hr class="line-right" /> <p class="panel-title">Chronologie</p> </div> <div class="zone-chrono"> <ul> <li><B>1898</B> Les Français Pierre et Marie Curie découvrent le polonium et le radium. </li> </ul> </div> </div> <div id="taboola-right-rail-encyclo-thumbnails" class="taboola"></div>  <div class="pub-pave oasm3"></div> </div> </div>  </div>  <div class="pub-bottom oasb"> </div>    <div class="footer"> <span class="footer-left"> <a href="/contenu/applications/applications_mobiles">Applications mobiles</a> <a href="/index">Index</a> <a href="/infos/credits">Mentions légales et crédits</a> <a href="/infos/cgu">CGU</a> <a href="/infos/cgv">CGV</a> <a href="/infos/confidentialite">Charte de confidentialité</a> <a class="optanon-show-settings">Cookies</a> <a href="/infos/contact">Contact</a> </span> <span class="footer-right"> <span>© Larousse</span> </span> </div>  </div> </body>      <script src="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js" integrity="sha384-aJ21OjlMXNL5UyIl/XNwTMqvzeRMZH2w8c5cRVpzpU8Y5bApTppSuUkhZXN0VxHd" crossorigin="anonymous"></script>     <script type="text/javascript" src="/library-web/slick/slick.min.js"></script>     <script type="text/plain" class="optanon-category-1"> //alert("CATEGORY-1: OK \nCookies strictement nécessaires"); 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