Neodymium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

60 praseodymium ← neodymium → promethium - ↑ Nd ↓ U Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	neodymium, Nd, 60
Chemical series	lanthanides
Group, Period, Block	n/a, 6, f
Appearance	silvery white, yellowish tinge
Atomic mass	144.242 (3) g/mol
Electron configuration	[Xe] 4f4 6s2
Electrons per shell	2, 8, 18, 22, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	7.01 g·cm−3
Liquid density at m.p.	6.89 g·cm−3
Melting point	1297  K (1024 ° C, 1875 ° F)
Boiling point	3347 K (3074 ° C, 5565 ° F)
Heat of fusion	7.14 kJ·mol−1
Heat of vaporization	289 kJ·mol−1
Heat capacity	(25 °C) 27.45 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 1595 1774 1998 (2296) (2715) (3336)
Atomic properties
Crystal structure	hexagonal
Oxidation states	3 (mildly basic oxide)
Electronegativity	1.14 (Pauling scale)
Ionization energies ( more)	1st: 533.1 kJ·mol−1
	2nd: 1040 kJ·mol−1
	3rd: 2130 kJ·mol−1
Atomic radius	185 pm
Atomic radius (calc.)	206 pm
Miscellaneous
Magnetic ordering	ferromagnetic
Electrical resistivity	( r.t.) (α, poly) 643 nΩ·m
Thermal conductivity	(300 K) 16.5 W·m−1·K−1
Thermal expansion	( r.t.) (α, poly) 9.6 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 2330 m/s
Young's modulus	(α form) 41.4 GPa
Shear modulus	(α form) 16.3 GPa
Bulk modulus	(α form) 31.8 GPa
Poisson ratio	(α form) 0.281
Vickers hardness	343 MPa
Brinell hardness	265 MPa
CAS registry number	7440-00-8
Selected isotopes
Main article: Isotopes of neodymium iso NA half-life DM DE ( MeV) DP 142Nd 27.13% Nd is stable with 82 neutrons 143Nd 12.18% Nd is stable with 83 neutrons 144Nd 23.8% 2.29×1015y α 1.905 140Ce 145Nd 8.3% Nd is stable with 85 neutrons 146Nd 17.19% Nd is stable with 86 neutrons 148Nd 5.76% Nd is stable with 88 neutrons 150Nd 5.64% 1.1×1019y β-β- 3.367 150Sm
References

Neodymium ( IPA: /ˌniːə(ʊ)ˈdɪmiəm, ˌniə(ʊ)-/) is a chemical element in the periodic table that has the symbol Nd and atomic number 60.

Notable characteristics

Neodymium, a rare earth metal, is present in misch metal to the extent of about 18%. The metal has a bright silvery metallic luster; however, being one of the more reactive rare earth metals, neodymium quickly tarnishes in air, forming an oxide that falls off and exposes the metal to further oxidation. Although belonging to rare earth metals, neodymium is not rare at all. It constitutes 38 ppm of Earth’s crust.

Applications

Uses of neodymium include

• Neodymium is a component of didymium used for colouring glass to make welder's goggles.
• Neodymium colours glass in delicate shades ranging from pure violet through wine-red and warm grey. Light transmitted through such glass shows unusually sharp absorption bands; the glass is used in astronomical work to produce sharp bands by which spectral lines may be calibrated. Neodymium is also used to remove the green colour caused by iron contaminants from glass.
• Neodymium salts are used as a colourant for enamels.
• Neodymium is used in the strongest permanent magnets known - Nd₂Fe₁₄B. These magnets are cheaper, lighter, and stronger than samarium-cobalt magnets. Neodymium magnets appear in high-quality products such as microphones, professional loudspeakers, in-ear headphones and computer hard disks where low mass, small volume, or strong magnetic fields are required.
• Probably because of similarities to Ca²⁺, Nd³⁺ has been reported to promote plant growth. Rare earth element compounds are frequently used in China as fertilizer.
• Size and strength of volcanic eruption can be predicted by scanning for neodymium isotopes. Small and large volcanic eruptions produce lava with different neodymium isotope composition. From the composition of isotopes, scientists predict how big the coming eruption will be, and use this information to warn residents of the intensity of the eruption.
• Certain transparent materials with a small concentration of neodymium ions can be used in lasers as gain media for infrared wavelengths (1054-1064 nm), e.g. Nd:YAG (yttrium aluminium garnet), Nd:YLF (yttrium lithium fluoride), Nd:YVO₄ (yttrium orthvanadate), and Nd:glass. The current laser at the UK Atomic Weapons Establishment (AWE), the HELEN 1-TW neodymium-glass laser, can access the midpoints of pressure and temperature regions and is used to acquire data for modelling on how density, temperature and pressure interact inside warheads. HELEN can create plasmas of around 10⁶ K, from which opacity and transmission of radiation are measured.
• Neodymium glass (Nd:Glass) solid-state lasers are used in extremely high power ( terawatt scale), high energy ( megajoules) multiple beam systems for inertial confinement fusion. Nd:Glass lasers are usually frequency tripled to the third harmonic at 351 nm in laser fusion devices.

Neodymium doped glass slabs used in extremely powerful lasers for inertial confinement fusion.

History

Neodymium was discovered by Baron Carl Auer von Welsbach, an Austrian chemist, in Vienna in 1885. He separated neodymium, as well as the element praseodymium, from a material known as didymium by means of spectroscopic analysis; however, it was not isolated in relatively pure form until 1925. The name neodymium is derived from the Greek words neos, new, and didymos, twin. Neodymium is frequently misspelled as neodynium.

Today, neodymium is primarily obtained through an ion exchange process of monazite sand ((Ce,La,Th,Nd,Y)PO₄), a material rich in rare earth elements, and through electrolysis of its halide salts.

Occurrence

Neodymium is never found in nature as the free element; rather, it occurs in ores such as monazite sand ((Ce,La,Th,Nd,Y)PO₄) and bastnasite ((Ce,La,Th,Nd,Y)(CO₃)F) that contain small amounts of all the rare earth metals. Neodymium can also be found in Misch metal; it is difficult to separate it from other rare earth elements.

Compounds

Neodymium compounds include

• Halides
  • NdF₃
  • NdCl₃
  • NdBr₃
  • NdI₃
• Oxides
  • Nd₂O₃
• Sulfides
  • NdS
  • Nd₂S₃
• Nitrides
  • NdN

Isotopes

Naturally occurring Neodymium is composed of 5 stable isotopes, ¹⁴²Nd, ¹⁴³Nd, ¹⁴⁵Nd, ¹⁴⁶Nd and ¹⁴⁸Nd, with ¹⁴²Nd being the most abundant (27.2% natural abundance), and 2 radioisotopes, ¹⁴⁴Nd and ¹⁵⁰Nd. In all, 31 radioisotopes of Neodymium have been characterized, with the most stable being ¹⁵⁰Nd with a half-life (T_½) of >1.1×10¹⁹ years, ¹⁴⁴Nd with a half-life of 2.29×10¹⁵ years, and ¹⁴⁷Nd with a half-life of 10.98 days. All of the remaining radioactive isotopes have half-lives that are less than 3.38 days, and the majority of these have half-lives that are less than 71 seconds. This element also has 4 meta states with the most stable being ¹³⁹Nd^m (T_½ 5.5 hours), ¹³⁵Nd^m (T_½ 5.5 minutes) and ¹⁴¹Nd^m (T_½ 62.0 seconds).

The primary decay mode before the most abundant stable isotope, ¹⁴²Nd, is electron capture and the primary mode after is beta minus decay. The primary decay products before ¹⁴²Nd are element Pr (praseodymium) isotopes and the primary products after are element Pm (promethium) isotopes.

Precautions

Neodymium metal dust is a combustion and explosion hazard.

Neodymium compounds, like all rare earth metals, are of low to moderate toxicity; however its toxicity has not been thoroughly investigated. Neodymium dust and salts are very irritating to the eyes and mucous membranes, and moderately irritating to skin. Breathing the dust can cause lung embolisms, and accumulated exposure damages the liver. Neodymium also acts as an anticoagulant, especially when given intravenously.

Neodymium magnets have been tested for medical uses such as magnetic braces and bone repair, but biocompatibility issues have prevented widespread application.