السماريوم Samarium هوعنصر كيميائي رمزه Sm ورقمه الذري 62.

الخصائص المميزة

السماريوم هوفلز أرضي نادر, ذوبريق فضي ساطع, وهومستقر بدرجة معقولة في الهواء; ويشتعل في الهواء عند درجة حرارة 150 °م. وحتى بالتخزين لمدد طويلة تحت زيت معدني, يتأكسد السماريوم بالتدريج, ويتكون مسحوق أصفر رمادي من الاكسيد-هيدروكسيد. ويتواجد ثلاثة تعديلات بلورية للفلز أيضاً, مع transformations عند 734 و922 °م.

الاستخدامات

استخدامات السماريوم تتضمن:

• اضاءة قوس الكربون لصناعة الصور المتحركة (مع فلزات الأرض النادرة الاخرى).
• بلورات CaF₂ للاستخدام في الميزرات الضوئية أوالليزرات.
• كممتص للنيوترونات في المفاعلات النووية.
• في السبائك والسماعات.
• Samarium-cobalt magnets; SmCo₅ and Sm₂Co₁₇ are used in making permanent magnet materials that have high resistance to demagnetization when compared to other permanent magnet materials. These materials have high coercivities and intrinsic coercivities. Samarium-cobalt combinations have recently found use in high-end magnetic pickups for guitars and related musical instruments.
• Samarium(II) iodide يـُستخدم as a chemical reagent in organic synthesis, for example in the Barbier reaction.
• Samarium oxide is used in optical glass to absorb infrared light.
• Samarium compounds act as sensitizers for phosphors excited in the infrared.
• Samarium oxide is a catalyst for the dehydration and dehydrogenation of ethanol.
• Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites.
• Radioactive Samarium-153 is used in medicine to treat the severe pain associated with cancers that have spread to bone. The drug is called "Quadramet".

تاريخ

السماريوم تم اكتشافه لأول مرة بواسطة مجهر طيفي spectroscopically في 1853 من قِبل الكيميائي السويسري جان شارل گاليسار ده ماريناك بسبب خطوط امتصاصها الحادة في الدايديميوم didymium، وفصله في باريس في عام 1879 الكيميائي الفرنسي پول إميل لكوك ده بوابودران من المعدن سمارسكيت ((Y,Ce,U,Fe)₃(Nb,Ta,Ti)₅O₁₆). وبالرغم من حتى السمارسكيت كان قد اُكتـُشِف لأول مرة في جبال الاورال، في أواخر عقد 1870، فإن ترسبات جديدة تم اكتشافها في نورث كارولينا، ومن ذلك المصدر اتى الدايديميوم الحامل للسماريوم.

معدن السمارسكيت سـُمـِّي على اسم ڤاسيلي سمارسكي-بيخوڤتس، رئيس أركان حرب (كولونل) سلاح مهندسي التعدين الروسي في 1845-1861. The name of the element is derived from the name of the mineral, and thus traces back to the name Samarsky-Bykhovets. In this sense samarium was the first chemical element to be named after a living person.

Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rods in some of the early nuclear reactors. Nowadays, a similar commodity product goes under the name of "Samarium-Europium-Gadolinium" concentrate (or SEG concentrate). This is prepared by solvent extraction from the mixed lanthanides extracted from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.

التواجد

السماريوم لا يتواجد في الطبيعة حراً, ولكن, مثل عناصر الأرض النادرة الأخرى, فهويتواجد متضمناً في الكثير من المعادن, ومنها مونازيت, باستناسيت وسمارسكيت; المونازيت (in which it occurs up to an extent of 2.8%) and bastnäsite are also used as commercial sources. Misch metal containing about 1% of samarium has long been used, but it was not until recent years that relatively pure samarium has been isolated through ion exchange processes, solvent extraction techniques, and electrochemical deposition. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride with sodium chloride or calcium chloride^[1]. Samarium can also be obtained by reducing its oxide with lanthanum.

المركبات

مركبات السماريوم تتضمن:

• الفلوريدات: ،
• الكلوريدات: ,
• البروميدات: ،
• اليوديدات: ,
• الأكسيدات:
• الكبريتيدات:
• السلنيدات:
• التلوريدات:

انظر أيضاً مركبات السماريوم.

النظائر

Naturally occurring samarium is composed ofخمسة stable isotopes, ¹⁴⁴Sm, ¹⁴⁹Sm, ¹⁵⁰Sm, ¹⁵²Sm and ¹⁵⁴Sm, and 2 extremely long-lived radioisotopes, ¹⁴⁷Sm (1.06×10¹¹y) and ¹⁴⁸Sm (7×10¹⁵y) and ,with ¹⁵²Sm being the most abundant (26.75% natural abundance).

Sm has a halflife of 90 years, and ¹⁴⁵Sm has a halflife of 340 days. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. This element also hasخمسة meta states with the most stable being ^141mSm (t_½ 22.6 minutes), ^143m1Sm (t_½ 66 seconds) and ^139mSm (t_½ 10.7 seconds).

The primary decay mode before the most abundant stable isotope, ¹⁵²Sm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before ¹⁵²Sm are element Pm (promethium) isotopes, and the primary products after are element Eu (europium) isotopes.

Natural Samarium has an activity of 128 Bq/g.

المحاذير

As with the other lanthanides, samarium compounds are of low to moderate toxicity, although their toxicity has not been investigated in detail.

المصادر

• Los Alamos National Laboratory - Samarium
• Centerwatch About drug Quadramet

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, UK, 1984.

وصلات خارجية

مشاع الفهم فيه ميديا متعلقة بموضوع Samarium.

• WebElements.com - Samarium
• It's Elemental - Samarium
• Reducing Agents > Samarium low valent