Hello everyone today, I want to tell you about the hardest metal on earth Chromium. As usual, let’s see where Roman is in the periodic table of chemical elements. There it is, hiding behind the Vanadium in the sixth group and yes I did not deceive you is true that Chromium has the highest hardness of all metals based of the Mohs scale that shows the resistance of a mineral to scratching. externally pure Chromium is a lustreless white metal that does not tarnish in air to demonstrate the main feature of chromium Namely its topmost hardness I’ll scratch an ordinary silicate glass with it. usual you cannot fool physics, Chromium easily scratch the surface of the glass leaving a clearly discernible markings. Also, I think that the hardness of Chromium is very much dependant of its purity. Metallic chromium is obtained from the chromium or mineral by reducing it using carbon to produce Ferrochromium an alloy of Chromium and Iron which is used in production of stainless steel. We will now turn to the chemical properties of Chromium, which this metal is highly enriched with even the name of the metal Chromium comes from the Greek “chroma” meaning color This name came to pass due to the fact that Chromium compounds can have almost all the colors of a rainbow. In laboratory the most common Chromium compound is Potassium dichromate it is used often in analytical chemistry or to clean chemical dishes from the very stubborn dirt also The substance is used as an intermediate compound in the production of chromium metal from ore. If you mix the potassium dichromate with any reducing agent for example aluminium powder and then ignited You’ll see a very violent reaction that will produce particles of chromium metal Potassium dichromate is very soluble in water In this compound Chromium has an oxidation state of blue 6 If you add a little bit of alkali i.e sodium hydroxide to the orange solution of potassium dichromate in an alkaline environment the dichromate will turn into chromate and Become yellow in the oxidation state of plus 6 Chromium may have a yellow and orange color Depending on the acidity of the environment however That’s not all if you add acid to the solution of potassium dichromate and also any reducing agent for example potassium metabisulfite There will be a reaction in which sulfur from metabisulfite will donate Electrons to chromium and will be restored to its trivalent state therefore Changing t’s colour to green compounds of trivalent chromium have a green color This is possible to prove with another reaction in order to do it Let’s take another orange chromium compound ammonium dichromate in which chromium also has an oxidation state of plus 6 now i’m Igniting this orange powder and where do we see ammonium dichromate started decomposing by itself? Forming a dark green substance chromium oxide due to the fact that formed chromium oxide has a porous particle structure it begins to occupy a larger volume and Over time it might seem that this green substance is being formed just out of nowhere I’m sorry to disappoint you But there are no miracles chromium oxide simply forms with nitrogen and water vapor That are also formed during this reaction as a result from a small amount of ammonium dichromate We got a whole pile of Corona oxide is a form of a date volcano Fun fact this reaction is actually called the volcano of ammonium dichromate the resulting chromium oxide is Better not to throw away as it can be easily used to make a gooey paste in The human oxide is the main component as an inert abrasive substance the Chromium an oxide has some unusual properties for example if you fill a flask with ammonia gas And then add some red hot chromium oxide in such conditions ammonia gas can react with oxygen Which under normal conditions does not occur in this reaction the chromium offset was the catalyst for the oxidation of ammonia in Oxygen also the chromium oxide can oxidize at another acidic aldehyde if you simply light a piece of a cotton wool Impregnated with ethanol the alcohol will just burn out however if you scatter the Chromium oxide over it It will limit assist of the oxygen in air when using the substance it’s possible to observe the residual glow This glow is caused by the oxidation of ethanol on the surface of the chromium oxide so called catalytic oxidation in which the ethanol is oxidized to acetic aldehyde Which has another specific smell? This smell is very Similar to the smell that can be felt in the morning after a hangover as the ethanol in our body is also oxidized to acetic aldehyde In addition to the trivalent compounds Chromium can also have divalent compounds for which we will now conduct another experiment Let’s take a test tube and for a solution of potassium dichromate in hydrochloric acid into it then we’ll add a few granules of zinc into the tube during the reaction of zinc with the hydrochloric acid Atomic hydrogen is formed which restores chromium from hexavalent state To trivalent and as a result the solution gradually becomes green atomic hydrogen is an extremely strong reducing agent and Because of that it gives away another electron to the chromium atom resultant in it becoming bivalent and the solution acquires a bluish color This color exactly is what the divalent Chromium compounds have So now we have a whole set of colored Chromium compound of different oxidation states true That’s not all Chromium compounds can also be used for another colorful experiment to create a flag in a test tube To conduct this experiment. We’ll need a solution of potassium dichromate Next we need diethyl ether Diethyl ether has a low density, so it will float on the surface of the solution of potassium dichromate next add a small amount of sulfuric acid solution to our mix and to start the reaction add a Few drops of 20 percent hydrogen peroxide into the test tube After adding the hydrogen peroxide a very interesting transformation occurs fluid between the layers of either and potassium dichromate Becomes dark when potassium from dichromate and hydrogen peroxide react in an acidic environment an unstable compound is formed chromium oxide peroxide that compound decomposes immediately in an aqueous solution and Gives a middle layer of the liquid this dark color however in Organic solvents such as diethyl ether Chromium oxide peroxide can be stabilized and for that reason the upper layer has a blue color I have no idea What country with the flag will these colours belong to. But, the reaction itself is quite colorful however when conducted these experiments it is worth remembering that the compounds of hexavalent chromium are extremely toxic But at the same time compounds of trivalent chromium are micro elements in our body such a two-faced is chromium pure metallic chromium is often included in the composition of stainless steel that has up to 30% of this metal the fact is that the metal Coromium is very resistance to the oxidation by airs Oxygen due to the tiny and very durable oxide film that covers the metal the same film of chromium oxide is formed on the surface of stainless steel That protects the metal from further oxidation at the end. We can say set in its pure form Chromium is a very hard metal true at the same time Having a huge range of compounds with a variety of colors you know you know a little bit more about one of the other metals if you would like to support a Continuous production of science videos like this one. 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