افتح القائمة الرئيسية

لانثانيد

(تم التحويل من اللانثنيدات)
Lanthanides in the periodic table
Hydrogen (reactive nonmetal)
Helium (noble gas)
Lithium (alkali metal)
Beryllium (alkaline earth metal)
Boron (metalloid)
Carbon (reactive nonmetal)
Nitrogen (reactive nonmetal)
Oxygen (reactive nonmetal)
Fluorine (reactive nonmetal)
Neon (noble gas)
Sodium (alkali metal)
Magnesium (alkaline earth metal)
Aluminium (post-transition metal)
Silicon (metalloid)
Phosphorus (reactive nonmetal)
Sulfur (reactive nonmetal)
Chlorine (reactive nonmetal)
Argon (noble gas)
Potassium (alkali metal)
Calcium (alkaline earth metal)
Scandium (transition metal)
Titanium (transition metal)
Vanadium (transition metal)
Chromium (transition metal)
Manganese (transition metal)
Iron (transition metal)
Cobalt (transition metal)
Nickel (transition metal)
Copper (transition metal)
Zinc (post-transition metal)
Gallium (post-transition metal)
Germanium (metalloid)
Arsenic (metalloid)
Selenium (reactive nonmetal)
Bromine (reactive nonmetal)
Krypton (noble gas)
Rubidium (alkali metal)
Strontium (alkaline earth metal)
Yttrium (transition metal)
Zirconium (transition metal)
Niobium (transition metal)
Molybdenum (transition metal)
Technetium (transition metal)
Ruthenium (transition metal)
Rhodium (transition metal)
Palladium (transition metal)
Silver (transition metal)
Cadmium (post-transition metal)
Indium (post-transition metal)
Tin (post-transition metal)
Antimony (metalloid)
Tellurium (metalloid)
Iodine (reactive nonmetal)
Xenon (noble gas)
Caesium (alkali metal)
Barium (alkaline earth metal)
Lanthanum (lanthanide)
Cerium (lanthanide)
Praseodymium (lanthanide)
Neodymium (lanthanide)
Promethium (lanthanide)
Samarium (lanthanide)
Europium (lanthanide)
Gadolinium (lanthanide)
Terbium (lanthanide)
Dysprosium (lanthanide)
Holmium (lanthanide)
Erbium (lanthanide)
Thulium (lanthanide)
Ytterbium (lanthanide)
Lutetium (lanthanide)
Hafnium (transition metal)
Tantalum (transition metal)
Tungsten (transition metal)
Rhenium (transition metal)
Osmium (transition metal)
Iridium (transition metal)
Platinum (transition metal)
Gold (transition metal)
Mercury (post-transition metal)
Thallium (post-transition metal)
Lead (post-transition metal)
Bismuth (post-transition metal)
Polonium (post-transition metal)
Astatine (metalloid)
Radon (noble gas)
Francium (alkali metal)
Radium (alkaline earth metal)
Actinium (actinide)
Thorium (actinide)
Protactinium (actinide)
Uranium (actinide)
Neptunium (actinide)
Plutonium (actinide)
Americium (actinide)
Curium (actinide)
Berkelium (actinide)
Californium (actinide)
Einsteinium (actinide)
Fermium (actinide)
Mendelevium (actinide)
Nobelium (actinide)
Lawrencium (actinide)
Rutherfordium (transition metal)
Dubnium (transition metal)
Seaborgium (transition metal)
Bohrium (transition metal)
Hassium (transition metal)
Meitnerium (unknown chemical properties)
Darmstadtium (unknown chemical properties)
Roentgenium (unknown chemical properties)
Copernicium (post-transition metal)
Nihonium (unknown chemical properties)
Flerovium (unknown chemical properties)
Moscovium (unknown chemical properties)
Livermorium (unknown chemical properties)
Tennessine (unknown chemical properties)
Oganesson (unknown chemical properties)


سلسلة اللانثـنيدات تتكون من 14 عنصر أرضي نادر تبدأ من سيريوم إلى لوتيتيوم في الجدول الدوري ، بالأرقام الذرية من 58 إلى 71 . وترجع تسمية سلسلة اللانثينيدات إلى عنصر اللانثانوم رغم أنه لا يوجد فيها . وتلى سلسة اللانثينيدات سلسة الأكتينيدات .

وتكون سلسلة اللانثينيدات هى السلسلة التى يكون فيها المدار f ممتلئ جزئيا أو كليا . بينما تكون المدارات الخارجية p و d فارغة . وحيث ان المدار f ليس نشيط كيميائيا مثل المدارات s و d و p ، فإن عناصر سلسلة اللانثينيدات تكون متشابها كيميائيا .

ويتم وضع سلسة اللانثينيدات تحت الجدول الدوري كما لو كانت تذييل له . بينما يوضح الجدول الدوري الطويل المكان الفعلى لمجموعة اللانثينيدات .

قالب:Periodic table (lanthanides)

الرقم الذري الإسم الرمز
58 سيريوم Ce
59 براسيوديميوم Pr
60 نيوديوم Nd
61 بروميثيوم Pm
62 ساماريوم Sm
63 يوروبيوم Eu
64 جادولينيوم Gd
65 تريبيوم Tb
66 ديسبروسيوم Dy
67 هولميوم Ho
68 إبريوم Er
69 ثوليوم Tm
70 اِيتربيوم Yb
71 لوتيتيوم Lu


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فهرست

Physical properties of the elements

Chemical element La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Atomic number 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
Image                            
Density (g/cm3) 6.162 6.770 6.77 7.01 7.26 7.52 5.244 7.90 8.23 8.540 8.79 9.066 9.32 6.90 9.841
Melting point (°C) 920 795 935 1024 1042 1072 826 1312 1356 1407 1461 1529 1545 824 1652
Boiling point (°C) 3464 3443 3520 3074 3000 1794 1529 3273 3230 2567 2720 2868 1950 1196 3402
Atomic electron configuration
(gas phase)*
5d1 4f15d1 4f3 4f4 4f5 4f6 4f7 4f75d1 4f9 4f10 4f11 4f12 4f13 4f14 4f145d1
Metal lattice (RT) dhcp fcc dhcp dhcp dhcp ** bcc hcp hcp hcp hcp hcp hcp fcc hcp
Metallic radius (pm) 162 181.8 182.4 181.4 183.4 180.4 208.4 180.4 177.3 178.1 176.2 176.1 175.9 193.3 173.8
Resistivity at 25 °C (μΩ·cm) 57–80
20 °C
73 68 64 88 90 134 114 57 87 87 79 29 79
Magnetic susceptibility
χmol /10−6(cm3·mol−1)
+95.9 +2500 (β) +5530(α) +5930 (α) +1278(α) +30900 +185000
(350 K)
+170000 (α) +98000 +72900 +48000 +24700 +67 (β) +183

* Between initial Xe and final 6s2 electronic shells

** Sm has a close packed structure like most of the lanthanides but has an unusual 9 layer repeat

Gschneider and Daane (1988) attribute the trend in melting point which increases across the series, (lanthanum (920 °C) – lutetium (1622 °C)) to the extent of hybridization of the 6s, 5d, and 4f orbitals. The hybridization is believed to be at its greatest for cerium, which has the lowest melting point of all, 795 °C.[1] The lanthanide metals are soft; their hardness increases across the series.[2] Europium stands out, as it has the lowest density in the series at 5.24 g/cm3 and the largest metallic radius in the series at 208.4 pm. It can be compared to barium, which has a metallic radius of 222 pm. It is believed that the metal contains the larger Eu2+ ion and that there are only two electrons in the conduction band. Ytterbium also has a large metallic radius, and a similar explanation is suggested.[2] The resistivities of the lanthanide metals are relatively high, ranging from 29 to 134 μΩ·cm. These values can be compared to a good conductor such as aluminium, which has a resistivity of 2.655 μΩ·cm. With the exceptions of La, Yb, and Lu (which have no unpaired f electrons), the lanthanides are strongly paramagnetic, and this is reflected in their magnetic susceptibilities. Gadolinium becomes ferromagnetic at below 16 °C (Curie point). The other heavier lanthanides – terbium, dysprosium, holmium, erbium, thulium, and ytterbium – become ferromagnetic at much lower temperatures.[3]


Chemistry and compounds

Chemical element La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Atomic number 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
Ln3+ electron configuration*[4] 4f0 4f1 4f2 4f3 4f4 4f5 4f6 4f7 4f8 4f9 4f10 4f11 4f12 4f13

4f14

Ln3+ radius (pm)[2] 103 102 99 98.3 97 95.8 94.7 93.8 92.3 91.2 90.1 89 88 86.8 86.1
Ln4+ ion color in aqueous solution[5] Orange-yellow Yellow Blue-violet Red-brown Orange-yellow
Ln3+ ion color in aqueous solution[4] Colorless Colorless Green Violet Pink Pale yellow Colorless Colorless V. pale pink Pale yellow Yellow Rose Pale green Colorless Colorless
Ln2+ ion color in aqueous solution[2] Blood red Colorless Violet-red Yellow-green

* Not including initial [Xe] core

Approximate colors of lanthanide ions in aqueous solution[2][6][7]
Oxidation state 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
+2 Sm2+ Eu2+ Tm2+ Yb2+
+3 La3+ Ce3+ Pr3+ Nd3+ Pm3+ Sm3+ Eu3+ Gd3+ Tb3+ Dy3+ Ho3+ Er3+ Tm3+ Yb3+ Lu3+
+4 Ce4+ Pr4+ Nd4+ Tb4+ Dy4+

Effect of 4f orbitals

Going across the lanthanides in the periodic table, the 4f orbitals are usually being filled. The effect of the 4f orbitals on the chemistry of the lanthanides is profound and is the factor that distinguishes them from the transition metals. There are seven 4f orbitals, and there are two different ways in which they are depicted: as a "cubic set" or as a general set. The cubic set is fz3, fxz2, fyz2, fxyz, fz(x2−y2), fx(x2−3y2) and fy(3x2−y2). The 4f orbitals penetrate the [Xe] core and are isolated, and thus they do not participate in bonding. This explains why crystal field effects are small and why they do not form π bonds.[4] As there are seven 4f orbitals, the number of unpaired electrons can be as high as 7, which gives rise to the large magnetic moments observed for lanthanide compounds.

Measuring the magnetic moment can be used to investigate the 4f electron configuration, and this is a useful tool in providing an insight into the chemical bonding.[8] The lanthanide contraction, i.e. the reduction in size of the Ln3+ ion from La3+ (103 pm) to Lu3+ (86.1 pm), is often explained by the poor shielding of the 5s and 5p electrons by the 4f electrons.[4]

 
Lanthanide oxides: clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium and gadolinium.

The electronic structure of the lanthanide elements, with minor exceptions, is [Xe]6s24fn. The chemistry of the lanthanides is dominated by the +3 oxidation state, and in LnIII compounds the 6s electrons and (usually) one 4f electron are lost and the ions have the configuration [Xe]4fm.[9] All the lanthanide elements exhibit the oxidation state +3. In addition, Ce3+ can lose its single f electron to form Ce4+ with the stable electronic configuration of xenon. Also, Eu3+ can gain an electron to form Eu2+ with the f7 configuration that has the extra stability of a half-filled shell. Other than Ce(IV) and Eu(II), none of the lanthanides are stable in oxidation states other than +3 in aqueous solution. Promethium is effectively a man-made element, as all its isotopes are radioactive with half-lives shorter than 20 years.

In terms of reduction potentials, the Ln0/3+ couples are nearly the same for all lanthanides, ranging from −1.99 (for Eu) to −2.35 V (for Pr). Thus these metals are highly reducing, with reducing power similar to alkaline earth metals such as Mg (−2.36 V).[2]


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Lanthanide oxidation states

The ionization energies for the lanthanides can be compared with aluminium. In aluminium the sum of the first three ionization energies is 5139 kJ·mol−1, whereas the lanthanides fall in the range 3455 – 4186 kJ·mol−1. This correlates with the highly reactive nature of the lanthanides.


 
Samples of lanthanide nitrates in their hexahydrate form. From left to right: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.


Hydrides


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Halides


Application Percentage
Catalytic converters 45%
Petroleum refining catalysts 25%
Permanent magnets 12%
Glass polishing and ceramics 7%
Metallurgical 7%
Phosphors 3%
Other 1%

The complex Gd(DOTA) is used in magnetic resonance imaging.


Donor Excitation⇒Emission λ (nm) Acceptor Excitation⇒Emission λ (nm) Stoke's Shift (nm)
Eu3+ 340⇒615 Allophycocyanin 615⇒660 320
Tb3+ 340⇒545 Phycoerythrin 545⇒575 235

Possible medical uses

Currently there is research showing that lanthanide elements can be used as anticancer agents. The main role of the lanthanides in these studies is to inhibit proliferation of the cancer cells. Specifically cerium and lanthanum have been studied for their role as anti-cancer agents.

One of the specific elements from the lanthanide group that has been tested and used is cerium (Ce). There have been studies that use a protein-cerium complex to observe the effect of cerium on the cancer cells. The hope was to inhibit cell proliferation and promote cytotoxicity.[20] Transferrin receptors in cancer cells, such as those in breast cancer cells and epithelial cervical cells, promote the cell proliferation and malignancy of the cancer.[20] Transferrin is a protein used to transport iron into the cells and is needed to aid the cancer cells in DNA replication. Transferrin acts as a growth factor for the cancerous cells and is dependent on iron. Cancer cells have much higher levels of transferrin receptors than normal cells and are very dependent on iron for their proliferation.[20]

Cerium has shown results as an anti-cancer agent due to its similarities in structure and biochemistry to iron. Cerium may bind in the place of iron on to the transferrin and then be brought into the cancer cells by transferrin-receptor mediated endocytosis.[20] The cerium binding to the transferrin in place of the iron inhibits the transferrin activity in the cell. This creates a toxic environment for the cancer cells and causes a decrease in cell growth. This is the proposed mechanism for cerium's effect on cancer cells, though the real mechanism may be more complex in how cerium inhibits cancer cell proliferation. Specifically in HeLa cancer cells studied in vitro, cell viability was decreased after 48 to 72 hours of cerium treatments. Cells treated with just cerium had decreases in cell viability, but cells treated with both cerium and transferrin had more significant inhibition for cellular activity.[20]

Another specific element that has been tested and used as an anti-cancer agent is lanthanum, more specifically lanthanum chloride (LaCl3). The lanthanum ion is used to affect the levels of let-7a and microRNAs miR-34a in a cell throughout the cell cycle. When the lanthanum ion was introduced to the cell in vivo or in vitro, it inhibited the rapid growth and induced apoptosis of the cancer cells (specifically cervical cancer cells). This effect was caused by the regulation of the let-7a and microRNAs by the lanthanum ions.[21] The mechanism for this effect is still unclear but it is possible that the lanthanum is acting in a similar way as the cerium and binding to a ligand necessary for cancer cell proliferation.

Biological effects

Due to their sparse distribution in the earth's crust and low aqueous solubility, the lanthanides have a low availability in the biosphere, and for a long time were not known to naturally form part of any biological molecules. In 2007 a novel methanol dehydrogenase that strictly uses lanthanides as enzymatic cofactors was discovered in a bacterium from the phylum Verrucomicrobia, Methylacidiphilum fumariolicum. This bacterium was found to survive only if there are lanthanides present in the environment.[22] Compared to most other nondietary elements, non-radioactive lanthanides are classified as having low toxicity.[23]

See also

References

  1. ^ Krishnamurthy, Nagaiyar and Gupta, Chiranjib Kumar (2004) Extractive Metallurgy of Rare Earths, CRC Press, ISBN 0-415-33340-7
  2. ^ أ ب ت ث ج ح خ Greenwood, N. N. (1997). Chemistry of the Elements (2nd Edition ed.). Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: extra text (link)
  3. ^ Cullity, B. D. and Graham, C. D. (2011) Introduction to Magnetic Materials, John Wiley & Sons, ISBN 9781118211496
  4. ^ أ ب ت ث Cotton, Simon (2006). Lanthanide and Actinide Chemistry. John Wiley & Sons Ltd.
  5. ^ Sroor, Farid M.A.; Edelmann, Frank T. (2012). "Lanthanides: Tetravalent Inorganic". Encyclopedia of Inorganic and Bioinorganic Chemistry. doi:10.1002/9781119951438.eibc2033. ISBN 9781119951438.
  6. ^ Holleman, p. 1937.
  7. ^ dtv-Atlas zur Chemie 1981, Vol. 1, p. 220.
  8. ^ Bochkarev, Mikhail N.; Fedushkin, Igor L.; Fagin, Anatoly A.; Petrovskaya, Tatyana V.; Ziller, Joseph W.; Broomhall-Dillard, Randy N. R.; Evans, William J. (1997). "Synthesis and Structure of the First Molecular Thulium(II) Complex: [TmI2(MeOCH2CH2OMe)3]". Angewandte Chemie International Edition in English. 36 (12): 133–135. doi:10.1002/anie.199701331.
  9. ^ Winter, Mark. "Lanthanum ionisation energies". WebElements Ltd, UK. Retrieved 2 September 2010.
  10. ^ أ ب Fukai, Y. (2005). The Metal-Hydrogen System, Basic Bulk Properties, 2d edition. Springer. ISBN 978-3-540-00494-3.
  11. ^ Kohlmann, H.; Yvon, K. (2000). "The crystal structures of EuH2 and EuLiH3 by neutron powder diffraction". Journal of Alloys and Compounds. 299 (1–2): L16–L20. doi:10.1016/S0925-8388(99)00818-X.
  12. ^ Matsuoka, T.; Fujihisa, H.; Hirao, N.; Ohishi, Y.; Mitsui, T.; Masuda, R.; Seto, M.; Yoda, Y.; Shimizu, K.; Machida, A.; Aoki, K. (2011). "Structural and Valence Changes of Europium Hydride Induced by Application of High-Pressure H2". Physical Review Letters. 107 (2): 025501. Bibcode:2011PhRvL.107b5501M. doi:10.1103/PhysRevLett.107.025501. PMID 21797616.
  13. ^ Tellefsen, M.; Kaldis, E.; Jilek, E. (1985). "The phase diagram of the Ce-H2 system and the CeH2-CeH3 solid solutions". Journal of the Less Common Metals. 110 (1–2): 107–117. doi:10.1016/0022-5088(85)90311-X.
  14. ^ Kumar, Pushpendra; Philip, Rosen; Mor, G. K.; Malhotra, L. K. (2002). "Influence of Palladium Overlayer on Switching Behaviour of Samarium Hydride Thin Films". Japanese Journal of Applied Physics. 41 (Part 1, No. 10): 6023–6027. Bibcode:2002JaJAP..41.6023K. doi:10.1143/JJAP.41.6023.
  15. ^ David A. Atwood, ed. (19 February 2013). The Rare Earth Elements: Fundamentals and Applications (eBook). John Wiley & Sons. ISBN 9781118632635.
  16. ^ Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford Science Publication. ISBN 978-0-19-855370-0.
  17. ^ Holleman, p. 1942
  18. ^ Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 125. ISBN 978-1-43981462-8. Retrieved 17 February 2014.
  19. ^ Ryazanov, Mikhail; Kienle, Lorenz; Simon, Arndt; Mattausch, Hansjürgen (2006). "New Synthesis Route to and Physical Properties of Lanthanum Monoiodide†". Inorganic Chemistry. 45 (5): 2068–2074. doi:10.1021/ic051834r. PMID 16499368.
  20. ^ أ ب ت ث ج Palizban, A. A.; Sadeghi-aliabadi, H.; Abdollahpour, F. (1 January 2010). "Effect of cerium lanthanide on Hela and MCF-7 cancer cell growth in the presence of transferring". Research in Pharmaceutical Sciences. 5 (2): 119–125. PMC 3093623. PMID 21589800.
  21. ^ Yu, Lingfang; Xiong, Jieqi; Guo, Ling; Miao, Lifang; Liu, Sisun; Guo, Fei (2015). "The effects of lanthanum chloride on proliferation and apoptosis of cervical cancer cells: involvement of let-7a and miR-34a microRNAs". BioMetals. 28 (5): 879–890. doi:10.1007/s10534-015-9872-6. PMID 26209160. S2CID 15715889.
  22. ^ Pol, A., et al (2014). "Rare Earth Metals Are Essential for Methanotrophic Life in Volcanic Mudpots". Environ Microbiol. 16 (1): 255–264. doi:10.1111/1462-2920.12249. PMID 24034209.
  23. ^ McGill, Ian (2005) "Rare Earth Elements" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim. doi:10.1002/14356007.a22_607.

Cited sources

  • Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (2007). Lehrbuch der Anorganischen Chemie (in الألمانية) (102 ed.). Walter de Gruyter. ISBN 978-3-11-017770-1.

وصلات خارجية

قالب:Periodic table (navbox)