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  • manganese is actually a much more interesting metal than you might expect.

  • I should say, Element, perhaps the metal.

  • So first thing we need to do is like the Bunsen so way All okay on then.

  • What we've got inside the boiling tube is actually potassium permanganate.

  • It is one of the transition metals on the road.

  • Transition metals stretches all the way from scanned him over here to zinc over there.

  • What makes manganese particularly interesting is that it is in the middle of this transition group.

  • There are 10 transition metals from scandal to sink on.

  • Dhe manganese is number five.

  • The reason they're 10 is because each of them has a certain number of de electrons.

  • One for Scandia Mlle 10 for zinc.

  • So Mangga knees in the middle has five and five.

  • If you're a mathematician, you will know is half 10.

  • So it has exactly half the number of the electrons that can be accommodated in the cell.

  • All I've gone and done, it's just popped a couple of spatulas off potassium permanganate into the boarding tube.

  • And as you can see from the color, it's a very, very dog, almost black, possibly a dark green.

  • So that's in there.

  • But let's begin just having looked at the metal itself.

  • This is a bottle of manganese that Neil has lent us, and Brady promised that we wouldn't break it.

  • Don't tell anyone, but I dropped it on a bit.

  • Has fallen out of the bottom.

  • Look, you break it, you broke It knew was gonna be very angry.

  • Anyway, let's look at the metal so you can see the metal is in this particular form.

  • It's coming sheets but has this rather bubbly features on the surface.

  • This is the top of where of the metals, and it's been broken up.

  • What is also interesting that I got magnet here and you can see it's not magnetic a tool, and you can't pick it up.

  • Now you've been asked, Why is it interesting if something's not magnetic?

  • Lots of things are not magnetic, and the reason that's interesting is if you look at it salts.

  • So this is assault of manganese.

  • The label is not very good, but it's manganese sulphate, M.

  • N s O.

  • For the first thing that you notice is that it is almost white.

  • It's very slightly pink, and this is surprising because, especially in your first chemistry lessons, they say the characteristic of the salt off transition metals is that they're colored.

  • And here's manganese sulfate almost white.

  • Remember that manganese metal is no magnetic.

  • Let's take the same magnet into the sulfate.

  • Push it down so you can see that the salt sticks to the magnet.

  • No, I think that's extraordinary.

  • Normally you don't expect salts to be magnetic, and it's even more surprising if the metal is not magnetic.

  • But the thought is off the safety flame into the hot blue flame.

  • Get so that it's at the tip over the flame.

  • It's nice and hot.

  • There you see our movement.

  • They're perfect, that movement there.

  • Or we could go right the way of the chief and I was dropping back down again on what's happened there in the heat.

  • We've changed the oxidation state off the manganese plus six.

  • So it's now okay too.

  • Mn four.

  • You're also getting oxygen, which is why you saw that movement off power does the gas is being liberated.

  • It it shot up to and you're getting manganese dioxide there.

  • And the reason why the salt is magnetic is because it has five electrons.

  • These five electrons in the D sell on their so called unpaid there, each in a different volume of space around the atom.

  • So each of them has a strong magnetic effect on with all five of them.

  • It's really magnetic.

  • The fact that it the material has no color is also associating with these five electrons.

  • If you drop a solution of manganese sulfate, which is also colorless, into sodium hydroxide solution, you get a precipitate of hydroxide.

  • And because there is aired dissolved in the sodium hydroxide, the oxygen removes one of the electrons from the manganese.

  • So it now is so called manganese three, which has only four electrons.

  • And it's nice brown color, So you suddenly get this color change.

  • This was one of the first experiments I did in my second year of university.

  • In a practical class, they didn't tell us what was happening.

  • We had to explain it.

  • And so now we need thio.

  • Make sure all of it is being converted Thio plus six oxidation states.

  • So I'm gonna make sure it stays in that flame for just that bit longer.

  • The really famous compound of manganese is protesting permanganate, which is a purple color potassium permanganate is K m a new four.

  • In fact, in the end, I know four minus the permanganate.

  • Manganese has no de electrons at all.

  • They've all gone to the oxygen.

  • And this very bright color is because the light makes one of the electrons jump back to the manganese.

  • So you get this very intense color, which is very bright.

  • Even a small amount of the material causes a lot of color.

  • And if you drop just a few tiny crystals of permanganate into water, you can see this beautiful purple color spreading out.

  • I persuaded Sam to repeat one of the earliest experiments.

  • I did myself after reading about it in the book heating, potassium permanganate.

  • And so, apart from that movement of the powder up and down the chief, it doesn't look like anything else is really happening.

  • I did this when I was 14 or 15.

  • Simon's using a nice boiling tube.

  • I used a metal spoon on a gas stove.

  • We're gonna put it into this centered funnel that's some top of the conical flask, and then I'm going to add some concentrated alkaline, and when you heat the permanganate it up There is a small puff of gas, but nothing very exciting.

  • But then you make so called potassium mangga Nate que tu m and No.

  • Four, which is all right green, if you put it in alkali solution.

  • So, Sam, if she's done what I suggested, has poured the solid out into a filter and then poured over it.

  • Some strong alkali.

  • And you should see this really nice Delta green color solution coming through.

  • I need to see that normally magnate in solution.

  • Are you just in water would go nice purple color, but here because you've got K to mn four, it's actually giving you a lovely green color.

  • But it's not a very stable compound, and if you add acid to the solution, it decomposes very quickly.

  • And so you get permanganate back again, plus a precipitate, which you may or may not be able to see of manganese dioxide, which is brown solid.

  • Now, When I did this experiment as a schoolboy in the kitchen, I didn't know all of this chemistry, and my sister's clothes were on the draining board of the Think they were being washed, and I'm ashamed to say.

  • And I didn't notice that some of the permanganate or Manda Nate got onto my sister's clothes and brown spots appeared all over it, and there was not very popular with my parents.

  • What were you punished?

  • I can't remember.

  • I think I was forgiven in the interests of science.

  • 13,487.

  • Drinking.

  • Was that?

  • Like I should You sure.

  • That is the biggest Brady number that appears in the 1st 1 million desperate places off pie.

manganese is actually a much more interesting metal than you might expect.

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錳 - 視頻週期表 (Manganese - Periodic Table of Videos)

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    林宜悉 發佈於 2021 年 01 月 14 日
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