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Praseodymium

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Praseodymium
Praseodymium
General Info
Atomic Symbol Atomic symbol::Pr
Atomic Number Atomic number::59
Atomic Weight Atomic weight::140.90765 g/mol
Chemical series lanthanide
Appearance grayish white
Sample of Praseodymium.jpg
Group, Period, Block 3, 6, f
Electron configuration [Xe] 4f3 6s2
Electrons per shell 2, 8, 18, 21, 8, 2
Electron shell praseodymium.png
CAS number CAS number::7440-10-0
Physical properties
Phase solid
Density Density::6.77 g/ml
Melting point Melting point::931 °C
Boiling point Boiling point::3512 °C
Isotopes of Praseodymium
iso NA half-life DT DE (MeV) DP
141Pr 100% 141Pr is stable with 82 neutrons.
141Pr syn 19.12 h β− 2.162 142Nd
142Pr syn 19.12 h ε 0.745 142Ce
143Pr syn 13.57 d β− 0.934 143Nd
All properties are for STP unless otherwise stated.

Praseodymium is the 59th chemical element in the Periodic Table of Elements. Elements such as this one would seem obscure and of no use, but even rare-earth elements such as this have uses. Praseodymium is a quite abundant element, even more abundant that something common like Tin.

It has many uses in today's world. The most notable thing Praseodymium lets humans do everyday is weld metals. By putting it in goggles it blocks very harmful ultra violet rays emitted by the sparks. Praseodymium is potentially a necessary agent in quantum computing for data storage. Praseodymium offers many uses, it lets us spark lighters, it even lets most of us watch color televisions.

Properties

A monazite crystal.

Praseodymium can be described as a soft, silvery-yellow, malleable material. In its pure form, it develops a green oxide that flakes off when exposed to atmospheric air. It must be stored under mineral oil or sealed from air [1]. Praseodymium reacts slower with oxygen than the other rare-earth metals, but it reacts rapidly with water [2].

Praseodymium reacts slowly with oxygen creating praseodymium (III,IV) oxide. Praseodymium burns at 150 °C causing it to oxidize much quicker.[3]

12Pr + 11O2 → 2Pr6O11

Praseodymium is electropositive. It reacts slowly with cold water and quickly with hot water forming praseodymium hydroxide, Pr(OH)3, and hydrogen gas (H2).[4]

2Pr(s) + 6H2O(g) → 2Pr(OH)3(aq) + 3H2(g)

Praseodymium can react with all halogens forming praseodymium(III) halides. The formulas for each reaction with their respective halogens is as follows:[5]

praseodymium(III) fluoride, PrF3
2Pr(s) + 3F2(g) → 2PrF3(s)
praseodymium(III) chloride, PrCl3
2Pr(s) + 3Cl2(g) → 2PrCl3(s)
praseodymium(III) bromide, PrBr3
2Pr(s) + 3Br2(g) → 2PrBr3(s)
praseodymium(III) iodide, PrI3
2Pr(s) + 3I2(g) → 2PrI3(s)

Praseodymium dissolves into diluted sulphuric acid to create solutions that contain aqueous Pr(III) ions with hydrogen gas.[6]

2Pr(s) + 3H2SO4(aq) → 2Pr3+(aq) + 3SO42-(aq) + 3H2(g)

Occurrences

Praseodymium is one of the most abundant rare-earth metals in existence. There is four times more of it than tin. Praseodymium is usually found in monazite and bastnasite ore. There is an estimated 2 million metric tons of Praseodymium in the earth today with humans manufacturing about 2,500 metric tons per year.[7]

The most common lanthanides, in order from most common to least common, are cerium, lanthanum, neodymium, and praseodymium. Although relatively abundant, it is quite hard to isolate it in its pure form because of how it is found in nature. Lanthanides are found in many different minerals, the most common of which are bastnaesite, monazite, and xenotime. Monazite is more difficult to work with when isolating because it contains thorium, which is radioactive, as is its decomposition products; and can cause a hazardous work environment.[8]

For many of its uses, praseodymium does not have to be isolated into its pure form making it easy to attain. At first, the metals were extracted from the ore with hydrochloric acid, sulphuric acid, and sodium hydroxide. In modern science, the techniques used to purify these lanthanide salt mixtures are much more thought out. They involve selective complexation techniques, solvent extractions, and ion exchange chromatography.[9]

Currently, the easiest way to isolate pure praseodymium is through the reduction of PrF3 with calcium metal.[10]

2PrF3 + 3Ca → 2Pr + 3CaF2

Uses

A pair of welding goggles made with Praseodymium

Praseodymium is used mostly as an alloying agent with magnesium in order to create strong metals for aircraft engines. It composes about 5% of Misch metal, which is used in lighter flints. Praseodymium is also used as the core for carbon arc lights. Salts made with Praseodymium give glasses and enamels a yellow color. Praseodymium filters out infrared radiation that can damage the eye so it is used to create didymium glass which is then used to make welder's goggles. [11] More recently, A silicate crystal doped with Praseodymium was used to slow down light to a few hundred meters per second. This discovery is very important to the development of the quantum computer. If invented, the quantum computer would revolutionize technology as we know it. [12] Praseodymium can also be found in color televisions and fluorescent lights.[13]

Effects on Health and Environment.

All rare earth metals are toxic in some way, praseodymium is of no exception. Praseodymium salts that dissolve in water are slightly toxic if they are ingested, but if the salt does not dissolve in water then its non toxic. Praseodymium can irritate the skin and eyes and is at the highest danger level when in a working environment. This is because gasses may be inhaled on the job site causing lung embolisms. Praseodymium can also threaten the liver if enough of it is in the human body.

Petrol-producing industries are the main reason praseodymium is exposed to the environment. It can also come in contact with the environment when things such as television sets and fluorescent lights are thrown away. Praseodymium will slowly gather in the soil and water leading to higher amount in humans, animals, and microorganisms. Praseodymium may damage the cell membranes of animals affecting their reproduction and nervous system. [14]

References