Encyclopedia > Gadolinium

  Article Content

Gadolinium

Europium - Gadolinium - Terbium
Gd
Cm  
 
 
General
Name, Symbol, NumberGadolinium, Gd, 64
Chemical series Lanthanides
Group, Period, Block_ [?], 6 , f
Density, Hardness 7901 kg/m3, no data
Appearance silvery white
Atomic properties
Atomic weight 157.25(3) amu
Atomic radius (calc.) 188 (233) pm
Covalent radius no data
van der Waals radius no data
Electron configuration [Xe]6s²5d¹4f7
e- 's per energy level2, 8, 18, 25, 9, 2
Oxidation states (Oxide) 3 (mildly basic)
Crystal structure Hexagonal
Physical properties
State of matter solid (ferromagnetic)
Melting point 1585 K (2394 °F)
Boiling point 3523 K (5882 °F)
Molar volume 19.90 ×10-3 m3/mol
Heat of vaporization 359.4 kJ/mol
Heat of fusion 10.05 kJ/mol
Vapor pressure 24400 Pa at 1585 K
Velocity of sound 2680 m/s at 293.15 K
Miscellaneous
Electronegativity 1.20 (Pauling scale)
Specific heat capacity 230 J/(kg*K)
Electrical conductivity 0.736 106/m ohm
Thermal conductivity 10.6 W/(m*K)
1st ionization potential 593.4 kJ/mol
2nd ionization potential 1170 kJ/mol
3rd ionization potential 1990 kJ/mol
4th ionization potential 4250 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
152Gd0.20%1.08E+14 a α2.205148Sm
154Gd2.18%154Gd is stable with 90 neutrons
155Gd14.80%155Gd is stable with 91 neutrons
156Gd20.47%156Gd is stable with 92 neutrons
157Gd15.65%157Gd is stable with 93 neutrons
158Gd24.84%158Gd is stable with 94 neutrons
160Gd21.86%1.3E+21 aβ-β-no data160Dy
SI units & STP are used except where noted.
Gadolinium is a chemical element in the periodic table that has the symbol Gd and atomic number 64.

Table of contents

Notable characteristics

Gadolinium is a silvery white, malleable and ductile rare earth metal with a metallic luster. It crystalizes in hexagonal, close-packed alpha form at room temperature; when heated to 1508 K, it transforms into its beta form, which has a body-centered cubic[?] structure.

Unlike other rare eart elements, Gadolinium is relatively stable in dry air; however, it tarnishes quickly in moist air and forms a losely adhering oxide that spalls off and exposes more surface to oxidation. Gadolinium reacts slowly with water and is soluble in dilute acid.

Gadolinium also has the highest thermal neutron capture cross-section of any (known) element, 49,000 barns[?], but it also has a fast burn-out rate, limiting its usefulness as a nuclear control rod[?] material.

Gadolinium becomes superconductive below a critical temperature of 1.083 K; it is strongly magnetic at room temperature, and is in fact the only metal to exhibit ferromagnetic properties except for fourth period transition metals.

Applications

Gadolinium is used for making gadolinium yttrium garnets[?], which have microwave applications; gadolinium compounds also are used for making phosphors for colour TV tubes, and solutions of compounds are used as intravenous contrasts to enhance images in patients undergoing magnetic resonance imaging. Gadolinium is also used for manufacturing compact discs and computer memory.

Gadolinium also possesses unusual superconductive properties, with as little as 1% of Gadolinium improving the workability and resistance of Iron, Chromium and related alloys to high temperatures and oxidation.

In the future, Gadolinium ethyl sulfate, which has extremely low noise characteristics, may be used in masers; furthermore, Gadolinium's high magnetic movement and its Curie temperature which lies just at room temperature suggest applications as a magnetic component for sensing hot and cold.

History

In 1880, Swiss chemist Jean Charles Galissard de Marignac[?] observed spectroscopic lines due to Gadolinium in samples of didymium[?] and gadolinite; French chemist Paul Émile Lecoq de Boisbaudran separated gadolinia[?], the oxide of Gadolinium, from Mosander's yttria[?] in 1886. The element itself was isolated only recently for the first time.

Gadolinium, like the mineral gadolinite, is named after Finnish chemist and geologist Johan Gadolin[?].

Biological role

Gadolinium has no known biological role, but is said to stimulate the metabolism.

Occurrence

Gadolinium is never found in nature as the free element, but is contained in many minerals such as gadolinite, monazite and bastnasite. Today, it is prepared by ion exchange[?] and solvent extraction[?] technique, or by the reduction of its anhydrous fluoride with metallic Calcium.

Compounds

Compounds of Gadolinium include:

Isotopes

Naturally occurring Gadolinium is composed of 5 stable isotopes, 154-Md, 155-Md, 156-Md, 157-Md and 158-Md, and 2 radioisotopes, 152-Md and 160-Md, with 158-Md being the most abundant (24.84% natural abundance). 30 radioisotopes have been characterized with the most stable being 160-Md with a half-life of 1.3E+21 years, 152-Md with a half-life of 1.08E+14 years, and 150-Md with a half-life of 1.79E+6 years. All of the remaining radioactive isotopes have half-lifes that are less than 74.7 years, and the majority of these have half lifes that are less than 24.6 seconds. This element also has 4 meta states with the most stable being 143m-Gd (t˝ 110 seconds), 145m-Gd (t˝ 85 seconds) and 141m-Gd (t˝ 24.5).

The primary decay mode before the most abundant stable isotope, 158-Gd, is electron capture and the primary mode after is beta minus decay. The primary decay products before 158-Gd are element Eu (Europium) isotopes and the primary products after are element Tb (Terbium) isotopes.

Precautions

All gadolinium compounds should be regarded as highly toxic. Gadolinium compounds are skin and eye irritants and perhaps carcinogenic. The metal dust presents a fire and explosion hazard.

External links



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
Afghanistan timeline January 1-16, 2002

... over eastern Afghanistan warning people not to shelter members of the Taliban and al Qaeda network or risk being bombed. Poland informed the United States that a ...