Palladium- a rare mineral, a noble metal of the platinum group, silvery in color, does not tarnish in air. Discovered by the English chemist and mineralogist W.Kh. Wollaston, who discovered palladium in native platinum in 1803. Malleable and malleable. More fusible than platinum, easily rolled and drawn into wire. Melting point 1552°C. Paramagnetic. Soluble in HNO 3 , in hot concentrated H 2 SO 4 and aqua regia. Palladium has an extremely high affinity for hydrogen, being able to absorb 900 times its own volume of hydrogen in powder form. Compared to other platinum metals, it is less resistant to oxidizing agents.

See also:

STRUCTURE

Palladium is a silver-white transition metal with a face-centered Cu-type lattice (a = 0.38902 nm; Z = 4; space group Fm3m). The unit cell of a face-centered cubic lattice is a cube with edge a. There are 8 atoms at the vertices of a cube. In addition, there is one atom in the center of each of the 6 faces.

PROPERTIES

Palladium is plastic, microadditives of nickel, cobalt, rhodium or ruthenium improve the mechanical properties of Pd and increase hardness.

Insoluble in water; density - 12.02 (20 ° C, g / cm³); under special conditions forms colloidal palladium and palladium black. Of all the metals of the platinum group, palladium is the most fusible. The melting point is 1554 ° C (in some sources 1552 ° C); boiling point around 2940 °C. Melting heat - 37.8 cal/g; specific heat capacity at 20 °C - 0.0586 cal/(g deg); specific electrical resistance at 25 ° C - 9.96 μOhm / cm; thermal conductivity - 0.161 cal/(cm sec deg). A paramagnet, that is, is magnetized in an external magnetic field in the direction of this field.

In its pure form, palladium has a beautiful silvery-white color. Like all precious metals, its color does not change with time.

Palladium in its purest form is a fairly soft metal. Its hardness is 373 MPa Brinell, which roughly corresponds to the hardness of platinum (392 MPa) and surpasses the hardness of gold and silver (245 MPa). The hardness of pure palladium increases when it is cold worked by forging or rolling. Upon annealing, the hardness decreases again. Pure palladium cannot be used in jewelry, they will be extremely sensitive to mechanical stress. However, adding small amounts of other metals to palladium, especially nickel or ruthenium, greatly increases its hardness. For example, for the production of jewelry in Europe and North America, 950 palladium is used, i.e. The jewelry contains 95% pure palladium. The remaining 5% is usually ruthenium or copper. In Russia, for the manufacture of jewelry, alloys of palladium with silver and nickel of 500 or 850 tests, an alloy with copper of 850 tests are used. The wear resistance of palladium jewelry is approximately equal to that of platinum and is higher than that of gold and silver jewelry.

RESERVES AND PRODUCTION

Geologists have calculated that palladium occupies a share of 6% in the bowels of the Earth. That is, this noble metal in the depths is twice as much as gold. Palladium is isolated from platinum, which means that it is mined in the same deposits.
Those are located on the Kola Peninsula, the Urals. Deposits near Norilsk have also recently been explored. In the platinum of these deposits, almost half of the palladium.
Outside of Russia, the lands of Alaska, Australia, Colombia, Canada, Africa are famous for the presence of valuable metal. The last two countries are rich in nickel ores. During their processing, palladium is also mined. Therefore, it is Africa and Canada that are leading in the production of this metal.
Deliveries of palladium in the world in 2007 amounted to 267 tons (including Russia - 141 tons, South Africa - 86 tons, USA and Canada - 31 tons, other countries - 9 tons). Palladium consumption in 2007 was 107 tons in the automotive industry, 40 tons in the electronics industry, and 12 tons in the chemical industry.

Palladium is mainly obtained from the processing of nickel, silver and copper sulfide ores.

ORIGIN

Palladium occurs as an admixture in many sulfides and silicates of ultramafic and mafic rocks. Some coals are enriched with palladium up to 10%, an increased concentration is observed in manganese ores, in phosphorites, in plant ash. The content of palladium is increased in ultramafic rocks and rocks containing Cu, Ni, and Te sulfides. Usually found in nature as an impurity in native platinum, with which it forms a disordered solid solution; sometimes found in its placers in the form of rounded grains. As a rule, it contains impurities of platinum, iridium, gold, silver. Palladium platinum contains 19-40% palladium, palladium stannoplatinum - 17-21%, polyxene - up to 6%, ferroplatinum - up to 13%, iridescent platinum - up to 4%. It can also be found as an admixture to native gold (in Brazil, for example, a rare variety of native gold (porpecite) was found, containing 8-11% palladium). It is formed in the zone of oxidation of primary sources of platinum and directly in placers as a result of hypergene transformation of platinum minerals. In iron meteorites, up to 7.7 grams per ton of matter. palladium, in stone - up to 3.5 gr.
Since placer deposits of native palladium are very rare, the main raw materials for its associated production are nickel and copper sulfide ores (Norilsk district, etc.)

APPLICATION

Palladium is often used as a catalyst, mainly in the process of fat hydrogenation and oil cracking. Palladium chloride is used as a catalyst and to detect trace amounts of carbon monoxide in air or gas mixtures.

Palladium chloride is used in electroplating as an activating agent in the galvanic metallization of dielectrics - in particular, the deposition of copper on the surface of laminated plastics in the production of printed circuit boards in electronics.

Palladium and palladium alloys are used in electronics for sulfide resistant coatings (an advantage over silver).
In particular, palladium is constantly consumed for the production of high-precision precision resistance rheochords (military and aerospace equipment), including in the form of an alloy with tungsten (for example, PdV-20M). The use in these nodes is due to the high wear resistance of palladium, which is ideal for its use in contact groups. By the way, rheochords made of palladium wire were widely used in civilian equipment, and palladium in its pure form was used in the contacts of step switches of control and recording machines, in contacts and strings of MKS (multiple coordinate connectors) ATSK (automatic coordinate telephone exchanges) manufactured with 1982 to 1987 USSR.
Palladium is also included in the composition of ceramic capacitors (KM type), with high rates of temperature stability of the capacitance in high-frequency broadcasting, radio communication, and television equipment.

In alloys used in jewelry (for example, to obtain an alloy of gold-palladium - the so-called "white gold"). Palladium, even at a low concentration in the alloy (about 1%), changes the color of the gold-based alloy from yellow to silvery white. The main alloys of palladium and silver used in jewelry are 500 and 850 silver (because they are the most technologically advanced in machining and decorative). Palladium is sometimes minted in limited edition commemorative coins.

Palladium and its alloys are used to make medical instruments, parts of pacemakers, dentures;
In some countries, a small amount of palladium is used to obtain cytostatic drugs - in the form of complex compounds, similar to cis-platinum.

Palladium - Pd

CLASSIFICATION

Strunz (8th edition)	1/A.14-20
Nickel-Strunz (10th edition)	1.AF.10
Dana (7th edition)	1.2.1.4
Dana (8th edition)	1.2.1.4
Hey's CIM Ref	1.66

Do you know what white gold is? It is an alloy of gold a small amount palladium.

We used to talk about nickel, and now the story about palladium is no less interesting and promising metal.

Palladium is a chemical element with atomic number 46 in the periodic system, denoted by the symbol Pd (lat. Palladium)

Palladium was discovered by the English chemist William Wollaston in 1803. Wollaston isolated it from platinum ore brought from South America. The name of the metal comes from the name of the asteroid Pallas, discovered by the German astronomer Olbergst in 1802. In turn, the asteroid is named after Pallas (Athena Pallas or her friend Pallas) from ancient Greek mythology.

Visually, palladium looks more like silver than platinum. This is his mystery. It has an attractive appearance, with a smooth, bewitching sheen. This is an aesthetic and "correct" metal. Palladium is easily polished, does not tarnish or corrode. Gems in a palladium frame look impressive and dignified. Palladium is the lightest of the platinum elements. And this is also one of its advantages as a jewelry metal.

Palladium (like platinum) is rarer than gold. About 200 tons of palladium are mined per year, and gold - 2500. Palladium is much lighter than platinum, it resembles gold in weight. Palladium 950 does not cause any allergic reactions. White color palladium is natural, i.e. not the result of coatings or alloys.

Palladium is identical to platinum in color, strength, clarity, beauty, and brilliance, but is less expensive.

In alloys used in jewelry (for example, to obtain an alloy of gold-palladium - the so-called "white gold"), palladium, even in a small amount (1%), can drastically change the color of gold to silver-white. Watches in white gold cases are popular abroad. The main alloys of palladium with silver in jewelry have a standard of 500 and 850 (the most technologically advanced and attractive).

By adding palladium to titanium or chromium steel, their high corrosion resistance becomes almost absolute. Jewelry from them, as well as from platinum, is practical and durable. In addition to standard palladium alloys, jewelry production sometimes uses decorative compounds of palladium with indium, which form a wide color scheme from golden to purple. While products from them - a rarity.

Heated palladium is well forged and welded. And at room temperature, it is soft and easy to process.

RECEIVING

Wollaston had to extract palladium from raw platinum, along the way mined during the washing of gold sands in distant Colombia. At that time the grain native platinum were the only mineral known to humans to contain palladium. About 30 minerals are now known to contain this element.

Like all platinum group metals, palladium is not widely used. Although with what to compare. It is calculated that in earth's crust it is about twice as much as gold. The largest placer deposits of platinum metals, and, consequently, of palladium, are located in our country (Urals), Colombia, Alaska and Australia. Small impurities of palladium are often found in gold sands.

But the main supplier of this metal was the deposits of nickel and copper sulfide ores. And, of course, processing such ores, precious palladium is extracted as a by-product. Extensive deposits of such ores have been found in the Transvaal (Africa) and Canada.

Explored in recent decades, the richest deposits of copper-nickel ores in the Arctic (Norilsk, Talnakh) have opened up great opportunities for further increasing the production of platinum metals and, first of all, palladium. After all, its content in such ores is three times greater than that of platinum itself, not to mention its other satellites.

The world's largest producer of palladium is OJSC MMC Norilsk Nickel.

APPLICATION

Catalysts

Palladium is often used as a catalyst, mainly in the process of fat hydrogenation and oil cracking. Palladium chloride is used as a catalyst and to detect trace amounts of carbon monoxide in air or gas mixtures.

Carbon monoxide CO is called carbon monoxide for a reason, it has no color, no taste, no smell. To determine the presence of CO in the air, you can use a piece of paper moistened with a solution of palladium chloride. This is a fail-safe signaling device; as soon as the CO content in the air exceeds the permissible level (0.02 mg/l), the paper turns black - PdCl2 is reduced to palladium black.

The market demand for palladium is mainly driven by the automotive industry. palladium is used in automotive exhaust catalytic converters.

Hydrogen Purification

Since hydrogen diffuses very well through palladium, palladium is used for deep cleaning hydrogen. Also, palladium is extremely efficient in reversibly accumulating hydrogen. To save expensive palladium in the production of membranes for hydrogen purification and separation of hydrogen isotopes, its alloys with other metals have been developed (the most efficient and economical alloy of palladium with yttrium).

Electroplating

Palladium chloride is used as an activating agent in the galvanic metallization of dielectrics - in particular, the deposition of copper on the surface of laminated plastics in the production of printed circuit boards in electronics.

Electrical contacts

Palladium and palladium alloys are used in electronics for sulfide resistant coatings. And also palladium is a part of ceramic capacitors, with high rates of temperature stability of the capacitance.

Other uses for palladium metal

Palladium is used for the manufacture of special chemical glassware, corrosion-resistant parts of high-precision measuring instruments.

Palladium and its alloys are used to make medical instruments, parts of pacemakers, dentures, and some medicines.

A certain amount of palladium is consumed for the manufacture of chemical equipment for the production of hydrofluoric acid (vessels, stills, pump parts, retorts).

Medications

In some countries, a small amount of palladium is used to obtain cytotoxic drugs.

Production and consumption indicators

Deliveries of palladium in the world in 2007 amounted to 267 tons (including Russia - 141 tons, South Africa - 86 tons, USA and Canada - 31 tons, other countries - 9 tons). Palladium consumption in 2007 was 107 tons in the automotive industry, 40 tons in the electronics industry, and 12 tons in the chemical industry.

And one more very valuable property

This property is the relative cheapness of palladium, which makes it perhaps the most promising of all platinum metals. Already, some alloys are reduced in price by adding palladium, for example, one of the alloys for the manufacture of dentures (it also contains copper, silver, gold and platinum). And the fact that palladium has become the most accessible of the platinum metals opens up an ever wider road for it in technology.

Long gone are the days when palladium was extracted in meager amounts from raw platinum alone. Now produced in the tens of tons a year, it is increasingly replacing platinum wherever possible.

named after Wollaston

Among the distinctions that mark the works of outstanding scientists of the world is the Wollaston medal, made of pure palladium. Established almost 150 years ago by the Geological Society of London, it was first minted in gold; then, in 1846, the famous metallurgist Johnson extracted pure palladium from Brazilian palladium gold, destined exclusively for the manufacture of this medal.

Charles Darwin was among the recipients of the Wollaston Medal. In 1943, the medal was awarded to Academician Alexander Evgenievich Fersman for his outstanding mineralogical and geochemical studies. Now this medal is kept in the State Historical Museum.

Palladium(Pd)
Atom properties
Thermodynamic properties of a simple substance

Most people think of gold, platinum and the like when they think of the phrase "precious metals". Few people remember other representatives of this group. Among such undeservedly forgotten precious metals is the element palladium. Despite its fame, which is much inferior to its "brothers", it is used in many industries and has very interesting properties.

History of discovery and name

The title of discoverer of palladium belongs to William Hyde Wollaston. In 1803, this English chemist succeeded in isolating a new element from South American platinum ore. The experiment in which Wollaston obtained palladium consisted of several stages:

The chemist named the discovered element in honor of Pallas, an asteroid discovered by a German astronomer a year before the discovery of Wollaston. The asteroid, in turn, got its name from the ancient Greek goddess Pallas Athena.

According to legend, the image of the goddess, called the palladium, fell from the sky. Once inside the walls of Troy, this talisman made her invincible. But after the palladium amulet was stolen, the great kingdom fell.

Characteristics and properties

In the periodic table of Mendeleev, palladium is located at number 46 in the tenth group (vertically) between nickel and platinum and in the fifth period (horizontally) between rhodium and silver. The accepted designation for this noble metal is Pd, derived from the Latin name Palladium.

Physical parameters

This rare element belongs to the transition metals and at the same time belongs to the platinum group of metals, also called light platinoids. It is known what palladium looks like in the form of a simple substance - under normal conditions, these are silver-white and very heavy crystals, characterized by:

• viscosity
• malleability;
• softness;
• plasticity.

The crystal lattice of a pure substance is a cubic syngony with a face-centered copper-type structure. The ability to improve the mechanical characteristics of palladium is possessed by:

• cobalt;
• nickel;
• rhodium;
• ruthenium.

In particular, microadditives of these elements significantly increase the hardness of the substance. Among the physical features, the density of palladium should be noted - under normal conditions it is 12 g/cm3. Judging by this indicator, the element is much closer to silver than to its “relative” platinum - the density of silver is 10.5 g / cm3, while that of platinum reaches 21 g / cm3.

As you know, in metals, the specific gravity is equal to their density. Thus, according to this indicator, the substance is closer to silver than to platinum. If we take the same jewelry made of palladium and platinum for comparison, the latter will be noticeably heavier.

Continuing the theme of weight, it is worth noting the molar (atomic) mass - it is 106.42 g / mol or daltons. The radius of an atom is 137 picometers, and the covalent radius reaches 128 picometers.

Palladium is a unique substance. It is the only one of all existing chemical elements whose outer electron shell is filled to the limit or maximum. The outer orbit of an atom of this metal holds 18 electrons.

It is impossible to dissolve a substance in water. It is also characterized by a fair refractoriness - the melting point of palladium is 1554 degrees Celsius. The temperature required for boiling reaches 2940 C. When special conditions are created, a substance can be transformed:

• in palladium black;
• to colloidal palladium.

This precious metal is paramagnetic, as it has a positive magnetic susceptibility. The electronegativity value on the Pauling scale is 2.20.

Chemical Features

The title of platinum metal with the highest chemical activity belongs to palladium. It does not react:

• with water;
• a solution of hydrogen nitride or ammonia;
• dilute acids and alkalis.

But on the other hand, it is able to react with hot concentrates of nitric and sulfuric acids, which distinguishes palladium from all other metals of the platinum group. At room temperature, the reaction of the substance starts:

• with wet bromine and chlorine;
• with royal vodka.

When fused with potassium hydrosulfate, palladium begins the process of oxidation. Reaction with molten sodium peroxide is also possible. Heating is the main condition for the implementation of a chemical reaction with many elements, including:

• silicon;
• arsenic;
• selenium;
• sulfur;
• tellurium;
• fluorine.

Upon contact with air during heating within the temperature range of 300-850 degrees, the light silver metal becomes dull, as an oxide film forms on its surface. At temperatures below 300 C, the metal remains stable, above 850 C, the film formed before that decomposes.

Isotopes and human exposure

Chemistry in many people causes negative associations, so it would be useful to focus on whether the metal has a harmful effect on humans or is safe.

Natural, created by nature element form six isotopes:

• 106Pd (27.34%);
• 108Pd (25.46%);
• 105Pd (22.34%);
• 110Pd (11.72%);
• 104Pd (11.14%);
• 102Pd (1%).

Isotopes are stable, so natural palladium is harmless. But there is also a variety created artificially. It is 107Pd, the longest-lived isotope of the element. It is radioactive and therefore dangerous. Its half-life is over seven million years.

Most of the isotopes are of natural origin. But a lot of them are also formed in reactors during the process of fission of plutonium and uranium nuclei. The formation of palladium in this way occurs gradually. Modern nuclear installations contain approximately 1.5 kg of palladium per 1 ton of nuclear fuel (assuming a 3% burnup).

Being in natural conditions

• nugget (allopalladium);
• minerals of the intermetallic type (stannopalladinite, palladium platinum, etc.);
• various compounds (braggite, palladinite, etc.).

There are about three dozen varieties of palladium minerals known to science. This element often acts as an accompaniment to other platinum metals. The content of the substance in the platinoid mixture ranges from 25–60% (depending on the deposit).

Native palladium is extremely rare. In my own way appearance it is almost indistinguishable from platinum. In addition to palladium, nuggets contain other elements:

• iridium;
• gold;
• platinum;
• silver.

According to Goldschmidt's geochemical classification of elements, palladium (along with all other platinoids) is one of the siderophiles. In other words, it has a characteristic affinity for iron and is concentrated in the earth's core.

Platinum and palladium are mined in two types of deposits:

• alluvial;
• indigenous.

The difference between these varieties from each other lies in the method of production. In deposits of primary type, metal is contained in minerals. In such places, the extraction of the substance is carried out by processing ores - copper or nickel. Palladium is recovered as a by-product.

Deposits of alluvial type are former primary deposits of ores. They have already been worked out, palladium has been released and has taken the form of nuggets.

Placer-type deposits where palladium can be mined account for about 2% of production worldwide. The largest of them are located in the Russian regions - in the Urals and the Far East, as well as abroad:

• in Australia;
• Colombia;
• Canada;

Predominant 98% of the mined palladium is extracted from the depths of the earth at the deposits of the primary type. The main mined ores are:

• copper-nickel;
• platinum;
• chrome.

Russia and South Africa have the status of leading countries in terms of the volume of world production of the precious metal at such deposits. The first place is occupied by the Norilsk Nickel enterprise - it accounts for almost half of the world's production volume. And the Bushveld complex (South Africa) owns the largest reserves of platinoids in the world.

Processing of ores is the main method for obtaining palladium, but not the only one. The element is recovered from recycled materials. This production method accounts for approximately 10% of the total world production.

Industries and Applications

Due to its characteristic properties - both physical and chemical - the element palladium is widely used in the electronics and chemical industries. To belong to precious metals led to the use of the substance as a material for jewelry.

It is worth noting that pure palladium jewelry cannot be found - they simply are not made. This metal is very soft - it can easily be stretched into a thin wire or rolled into foil, but any metal product without impurities will not withstand even a weak load. Therefore, even at the production stage, small fractions of other metals are added to the material.

In the wide use of palladium, the key role was played by the fact that this element can be processed by any method and used in a wide variety of forms, types, etc. To visually assess the scale of the use of the metal, it is worth distributing the areas by percentage:

• 70% - automotive industry;
• 10% - electronics production;
• 5% (for each) - chemical industry, medicine, investment;
• 5% (in total) - jewelry, coinage, etc.

V Lately the use of palladium as an investment is gaining popularity. The value of this noble metal is very high, it is involved in exchange trading, so such an investment of money can be quite profitable.

However, not every owner of palladium brings happiness. For the acquisition, storage and sale of an illegal nature, the prescribed criminal punishment will necessarily follow - imprisonment for a maximum of 5 years.

In 2015, employees of the FSB detained Omsk City, in whose garage 1.5 kg of catalysts with palladium worth 2 million rubles were stored. Where and how the violator of the law managed to get such a quantity of palladium catalysts is unknown, but this one interesting fact from modern history palladium proves that the pursuit of illegal gain will sooner or later backfire.

DEFINITION

Palladium located in the fifth period of the VIII group of the secondary (B) subgroup of the Periodic Table.

Relates to elements d-families. Metal. Designation - Pd. Ordinal number - 46. Relative atomic mass- 106.4 amu

Electronic structure of the palladium atom

The palladium atom consists of a positively charged nucleus (+46), inside which there are 46 protons and 60 neutrons, and 46 electrons move around in five orbits.

Fig.1. Schematic structure of the palladium atom.

The distribution of electrons in orbitals is as follows:

46Pd) 2) 8) 18) 18) 0 ;

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 5s 0 .

The valence electrons of the palladium atom are those located on 4 d- and 5 s-orbitals. The energy diagram of the ground state takes the following form:

The valence electrons of a palladium atom can be characterized by a set of four quantum numbers: n(chief quantum), l(orbital), m l(magnetic) and s(spin):

sublevel

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Exercise	How many atomic orbitals d— is the sublevel filled for elements with serial numbers 43 and 76? Write down their electronic formulas.
Solution	There are five orbitals on the d-sublevel, each of which can simultaneously contain 2 electrons (10 in total). Elements with atomic numbers 43 and 76 are technetium (Tc) and osmium (Os). Let us write down the electronic configurations of their atoms in the ground state: 43 Tc 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4 d 5 5 s 2 ; 76 Os 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 10 4f 14 5s 2 5p 6 5d 6 6s 2 . In the technetium atom, all 5 orbitals of the 4d sublevel are filled, but not completely, as well as in the osmium atom, all (5 orbitals of the 5d sublevel).
Answer	5 and 5.