User:Praseodymium-141/Neodymium/properties

Physical properties
Neodymium is the fourth member of the lanthanide series. It has a melting point of 1024 C and a boiling point of 3074 C. Metallic neodymium has a bright, silvery metallic luster.

Neodymium commonly exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at about 863 °C. Neodymium, like most of the lanthanides, is paramagnetic at room temperature and becomes an antiferromagnet upon cooling to 20 K.

Neodymium is a rare-earth metal that was present in the classical mischmetal at a concentration of about 18%. To make neodymium magnets it is alloyed with iron, which is a ferromagnet.

Electron configuration
In the periodic table, it appears between the lanthanides praseodymium to its left and the radioactive element promethium to its right, and above the actinide uranium. Its 60 electrons are arranged in the configuration [Xe]4f46s2. Like most other metals in the lanthanide series, neodymium usually only uses three electrons as valence electrons, as afterwards the remaining 4f electrons are strongly bound: this is because the 4f orbitals penetrate the most through the inert xenon core of electrons to the nucleus, followed by 5d and 6s, and this increases with higher ionic charge. Neodymium can still lose a fourth electron because it comes early in the lanthanides, where the nuclear charge is still low enough and the 4f subshell energy high enough to allow the removal of further valence electrons.

Chemical properties
Neodymium, like other lanthanides, usually has the oxidation state +3, but it can also form in the +2 and +4 oxidation states, and even, in very rare conditions, +0. Neodymium metal quickly oxidizes at ambient conditions, forming an oxide layer like iron rust that spalls off and exposes the metal to further oxidation; a centimeter-sized sample of neodymium corrodes completely in about a year. Like its neighbor praseodymium, it readily burns at about 150 °C to form neodymium(III) oxide; the oxide peels off, exposing the bulk metal to the further oxidation:
 * 4Nd + 3O2 → 2Nd2O3

Neodymium is a quite electropositive element, and it reacts slowly with cold water, or quickly with hot water, to form neodymium(III) hydroxide:
 * 2Nd (s) + 6H2O (l) → 2Nd(OH)3 (aq) + 3H2 (g)

Neodymium metal reacts vigorously with all the stable halogens:


 * 2Nd (s) + 3F2 (g) → 2NdF3 (s) [a violet substance]
 * 2Nd (s) + 3Cl2 (g) → 2NdCl3 (s) [a mauve substance]
 * 2Nd (s) + 3Br2 (g) → 2NdBr3 (s) [a violet substance]
 * 2Nd (s) + 3I2 (g) → 2NdI3 (s) [a green substance]

Neodymium dissolves readily in dilute sulfuric acid to form solutions that contain the lilac Nd(III) ion. These exist as a [Nd(OH2)9]3+ complexes:


 * 2Nd (s) + 3H2SO4 (aq) → 2Nd(3+) (aq) + 3SO4(2-) (aq) + 3H2 (g)

Compounds

 * Neodym(III)sulfat.JPGNeodymium(III) acetate.jpg Neodymium(III)_hydroxide.jpg

Some of the most important neodymium compounds include:
 * halides: NdF3; NdCl2; NdCl3; NdBr3; NdI2; NdI3
 * oxides: Nd2O3
 * hydroxide: Nd(OH)3
 * carbonate: Nd2(CO3)3
 * sulfate: Nd2(SO4)3
 * acetate: Nd(CH3COO)3
 * neodymium magnets (Nd2Fe14B)

Some neodymium compounds have colors that vary based on the type of lighting.

Organoneodymium compounds
Organoneodymium compounds are compounds that have a neodymium–carbon bond. These compounds are similar to those of the other lanthanides, characterized by an inability to undergo π backbonding. They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric.

Isotopes
Naturally occurring neodymium (60Nd) is composed of five stable isotopes—142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% of the natural abundance)—and two radioisotopes with extremely long half-lives, 144Nd (alpha decay with a half-life (t1/2) of 2.29×1015 years) and 150Nd (double beta decay, t1/2 ≈ 7×1018 years). In all, 33 radioisotopes of neodymium have been detected, with the most stable radioisotopes being the naturally occurring ones: 144Nd and 150Nd. All of the remaining radioactive isotopes have half-lives that are shorter than twelve days, and the majority of these have half-lives that are shorter than 70 seconds; the most stable artificial isotope is 147Nd with a half-life of 10.98 days.

Neodymium also has 13 known metastable isotopes, with the most stable one being 139mNd (t1/2 = 5.5 hours), 135mNd (t1/2 = 5.5 minutes) and 133m1Nd (t1/2 ~70 seconds). The primary decay modes before the most abundant stable isotope, 142Nd, are electron capture and positron decay, 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. Four of the five stable isotopes have been predicted to decay to isotopes of cerium or samarium and are only observationally stable. Additionally, some observationally stable isotopes of samarium are predicted to decay to isotopes of neodymium.

Neodymium isotopes are used in various scientific applications. 142Nd has been used for the production of short-lived Tm and Yb isotopes. 146Nd has been suggested for the production of 147Pm, which is a source of radioactive power. Several neodymium isotopes have been used for the production of other promethium isotopes. The decay from 147Sm (t1/2 = 1.06 × 1011) to the stable 143Nd allows samarium–neodymium dating. 150Nd has also been used to study double beta decay.