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So today I will tell you about the most rare metal on Earth - iridium.
Iridium is a transitional metal, which is located in the middle of the periodic table, below rhodium. If we take a look at the prevalence of all elements in the earth's crust, Iridium holds the last place, that is a billion atoms of all that there is and only one atom of iridium. This metal is 40 times rarer than gold.
In much higher concentrations iridium is found in meteorites and also in the depths of the Earth, in magma. Interestingly enough, in the layers of rock sediments, though more precisely in the formation of clay, that is aged about 66 million years there were found high concentrations of iridium and this can indicate the collision of Earth with a huge meteorite in the past, which in theory was the cause of the death of the dinosaurs. In it’s appearance iridium is a shiny metal that does not oxidize in air.
This metal has almost the highest density of all metals, just 0.12% lower than that of osmium - the most dense metal.
In this tiny tiny metal droplet, which is of the size of a match head, we have 1 gram of iridium. To help you understand how high is the density of iridium, I will show other metals with the same mass for comparison.
Lead, copper, gallium, zinc, magnesium, and the lightest metal - lithium.
The volumes of the first and last metal differ by about 30 times, although their mass is the same. Iridium is also a very hard metal that is firmer than the solid steel in 1.5 (one and a half) times. Iridium, in addition to its rarity is even the most stable metal that does not oxidize in air up to 2000 degrees, and is not soluble in either acid or aqua regia. Iridium can only react with the fluorine at temperatures of about 600 degrees.
Unfortunately, due to the low activity of iridium, I cannot conduct any chemical experiments or have quality reactions with it.
The only thing that I can do is make a fine powder of iridium and set it on fire in the air, but as you can see, in this case iridium dust is burning quite slowly and also requires dispersing it in the air. For the first time on youtube, you can observe a burning iridium. Also, due to the low activity of iridium, the metal does not tarnish in air, even when heated to above 1,000 degrees. The only thing that the drop of iridium got covered with is a partially evaporated ceramic layer, the one that the forceps are made from. Iridium compounds are can be either brown or yellow, such as the complex of Vasca, which is used as a catalyst in organic chemistry.
By the way, Iridium is the only element that can give away 9 electrons and form compounds with +9 (plus nine) oxidation state.
Iridium now finds many uses in science and technology.
In most cases, we will probably find iridium in spark plugs for vehicles, due to the high stability of iridium to oxidation under the influence of electric discharge.
Pure iridium is used for making crucibles for growing single crystals, foil for making non-amalgam cathodes, as well as as a part of the highly resistant to corrosion alloys.
The first standard of mass of one kilogram was created in 1889 using an alloy composition of 90% platinum and 10% iridium and is called the International Prototype Kilogram, it is still kept in the Paris Chamber of Weights and Measures.
Now you know more about one more of the elements, if you would like the scientific series of the elements to continue, please subscribe to my channel and also throw in some likes if you can! Thank you for watching.