Structures of Compounds of Transition Metals
This is a modal window.
The media could not be loaded, either because the server or network failed or because the format is not supported.
Formal Metadata
| Title |
| |
| Title of Series | ||
| Number of Parts | 340 | |
| Author | ||
| License | CC Attribution - NonCommercial - NoDerivatives 4.0 International: You are free to use, copy, distribute and transmit the work or content in unchanged form for any legal and non-commercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor. | |
| Identifiers | 10.5446/55123 (DOI) | |
| Publisher | ||
| Release Date | ||
| Language |
Content Metadata
| Subject Area | ||
| Genre | ||
| Abstract |
|
Lindau Nobel Laureate Meetings164 / 340
3
5
15
16
18
22
23
27
32
33
34
35
47
54
58
67
69
70
72
73
78
79
83
84
85
86
87
90
92
95
100
102
103
104
105
106
114
115
116
118
119
120
122
126
128
129
130
131
133
137
142
143
145
147
148
149
153
155
156
159
162
163
165
168
169
174
176
178
181
182
189
194
198
201
202
203
206
209
213
214
217
218
219
220
225
227
228
237
240
241
244
245
250
254
257
260
261
266
273
278
284
285
287
291
293
297
302
308
310
317
318
319
321
325
327
328
333
00:00
NobeliumSystemic therapyDeterrence (legal)Wasserwelle <Haarbehandlung>IronPalladiumSea levelChemistrySurface scienceFunctional groupGolgi apparatusAtomChemical structureÖlElectronIonenbindungAddition reactionSet (abstract data type)Atomic orbitalErdrutschCobaltElectronic cigaretteDynamiteCovalent bondController (control theory)Hydrogen bondInitiation (chemistry)Activity (UML)TetraederstrukturCarcinoma in situPlatinExplosionCalculus (medicine)Carbon (fiber)Transition metalSeparation processWine tasting descriptorsMethanisierungChemical bondBase (chemistry)SpeciesChemical plantDreifachbindungAzo couplingDoppelbindungHexamethylenetetramineMultiprotein complexResonance (chemistry)Emission spectrumCHARGE syndromeKohlenstoff-14ChemistWaterSetzen <Verfahrenstechnik>BerylliumAtomic numberHybridisierung <Chemie>MoleculePhysical chemistryValence (chemistry)Organische ChemieChemical engineeringHydrogenMolecular geometryChemical compoundPeriodateScurvyStickstoffatomHope, ArkansasSpinning (polymers)DessertAqueous solutionMan pageChemical elementIce sheetTidal raceAtomic orbitalFaserplatteRiver sourceCondensationPotenz <Homöopathie>Langmuir, IrvingGermanic peoplesEthyleneNutrientMeteoriteThermoformingSmoking (cooking)CooperativityMolecularity
Transcript: English(auto-generated)
00:11
Twenty years roughly, I've been dividing my time about equally among three activities. One has been work in chemistry, especially structural chemistry.
00:28
The second has been work for world peace and against nuclear weapons or against war in general. And the third has been work in the field of nutrition in relation to health, and especially
00:46
the vitamins, and in particular, vitamin C in relation to cancer, especially.
01:02
A month or two ago, there was an article in a magazine called Hospital Medicine. It was an interview with me, and it ended with a question that the interviewer had put to me.
01:21
He said, are you hopeful that the world will not be destroyed in a nuclear war? And I said, well, of course I'm hopeful. You can see that I have hope. Otherwise, I wouldn't be wasting my time talking about nuclear war, nuclear weapons,
01:42
and the destruction of civilization, but I'm just enjoying myself. So he said, how would you be enjoying yourself? And I said, by making quantum mechanical calculations about nuclear structure. So I put down that here I would enjoy myself by talking about the structure of compounds
02:08
of the transition metals. It's the sort of thing that interests me, that I like to do. But of course, this problem of world peace or possible destruction of civilization or
02:26
even bringing the human race to an end is such an important one that I feel that I need to say something about it. In fact, I'm pleased to do so. In December 1947, my wife and children and I were on our way to Europe on the
02:48
15th of May, and I got out a sheet of cardboard, which was an announcement of a speech that I was to give or had given in Cornell or Princeton.
03:03
I've forgotten where. And on the back of it, I wrote a vow that in every lecture that I gave from then on, I would say something about world peace. Well, you know, I didn't really live up to the vow. Sometimes I would forget to say anything about world peace.
03:23
But I remember it now. It's been impressed on me by circumstances, by our having President Reagan in the White House, for example. Things are worse now than they were even a few years ago.
03:51
Twenty-five years ago in 1958, I got out a book, No More War.
04:01
And now twenty-five years have gone by. It came out two weeks ago, the 15th of June, in a revised edition, the 25th anniversary edition of this book, No More War. When the publisher asked me to revise it, I looked over the ten chapters.
04:25
I thought, here, things haven't changed very much. The world has become more dangerous. The situation has become more dangerous. But the arguments are essentially just what they were twenty-five years ago. So I don't see that I can improve it.
04:44
I thought the writing was pretty good, too. I don't see anything wrong with the English. So what can I do? Well, the ten chapters are reprinted just the way that they were printed twenty-five years ago. But then there is an addendum of five pages, roughly, at the end of each of the chapters
05:04
and a couple of additional appendices at the end of the book. I was astonished when I looked at this book and looked at the printed accounts of lectures that I was giving around twenty-five years ago at the fact that the stockpiles of nuclear
05:28
weapons have not increased in magnitude. Twenty-five years ago, I said that the United States and the Soviet Union together and with a little contribution from Britain and France have sixty thousand megatons of
05:46
nuclear weapons. And my estimate now is sixty thousand megatons. There's been a great increase in the number of individual nuclear weapons. Almost everybody sells some various authorities that the United States now has thirty thousand
06:07
warheads of the Soviet Union, twenty thousand. President Reagan's policy is that we build seventeen thousand more in the next few years. But the warheads are smaller now than they were twenty years, twenty-five years ago.
06:25
We had a few thousand twenty megaton warheads then. Now we have United States and Soviet Union, fifty thousand, which run around one megaton each. What happened?
06:40
Well, what happened is that somebody in the Bureau of the Budget said, here you have these thousands of twenty megaton bombs. One twenty megaton bomb exploded over New York, it is estimated, would kill at least ten million people. How many targets are there in the Soviet Union that justify exploding a twenty megaton bomb?
07:05
Why not save money by tailoring them to the size of the target? And so the MIRV system was introduced and we began with these multiple warheads carrying smaller, these rockets that would carry smaller warheads and be independently directed toward
07:26
various targets suited to a one megaton or even a five hundred kiloton bomb. I got pretty worried the other day when I saw an advertisement by an oil company,
07:41
and I can't remember why the advertisement was what it was, but it showed a picture of a small city devastated by an explosion with ordinary explosives. Perhaps, well, the advertisement said four hundred and fifty seven megaton, no, four
08:02
hundred and fifty seven tons of dynamite exploded with megaton light. I thought, here the officers of this oil company are pretty smart people. The people who work for the advertising agency, no doubt, are pretty smart people.
08:23
And yet they make an error of more than two thousand fold in the magnitude of a megaton. A megaton is not four hundred and fifty seven tons of dynamite or TNT. It's a million tons, more than two thousand times as much as four hundred and fifty seven
08:45
tons. And if these people, these smart people, are off by a two thousand fold in understanding what nuclear war is about, then the people as a whole are off by that much in understanding
09:01
what nuclear war is about, including the people in Germany. Now, in nineteen fifty eight, Joseph Roetblatt, professor of physics in the University of London and the secretary, general secretary for the Pugwash conferences for many years, Roet discussed his estimate of what
09:26
a nuclear war would be like. He said that the initial attack would involve ten thousand or fifteen thousand megatons and the counterattack would involve ten thousand or fifteen thousand megatons, a total of twenty thousand or thirty thousand megatons. The
09:48
other people who have analyzed the effects of nuclear war have almost always also said, also discussed the attacks by ten thousand megatons by each side on the other side.
10:07
So, we can expect that a nuclear war would involve twenty thousand or thirty thousand megatons. This means, well, what does that mean? The Second World War was a six megaton war.
10:24
The whole of the second war involved six million tons of high explosives, so that a nuclear war, if it were fought, would involve between three thousand and five thousand,
10:44
is that right? Six into twenty thousand is about three thousand, six into thirty thousand, about five thousand, between three thousand and five thousand times the destructive power of the whole of the Second World War and condensed into a single day, not spread out over five years.
11:05
You can understand why scholars who, scientists who investigate these matters try to make predictions feel that almost certainly civilization would be destroyed, and perhaps the
11:21
human race would be, would cease to exist, and most other species of animals. Perhaps the smoke and dust would obscure the surface of the earth from the sunlight in the same way that the dust from the meteorite that struck the world sixty-five million years ago
11:44
led to the great extinction when all of the dinosaurs died, all species of dinosaurs, all eighteen species, and most species of animals and plants that were in existence ceased to exist. Most living organisms on earth ceased to exist. Well, life continued after that
12:08
great extinction, but the dinosaurs didn't continue. Human beings might well not continue to exist. What have we done in the last twenty-five years? We have made these systems
12:24
more and more complicated so that there is a greater and greater probability that some accident would occur that would initiate this ultimate catastrophe.
12:42
I find it hard to believe that the world is in this insane state that it is in now, and that the United States would continue to spend the hundreds of billions of dollars per year in this really irrational manner. I think that it's a good thing that nuclear weapons were
13:09
developed. We had the First World War with twenty or thirty million people killed, and the Second World War with forty or fifty million people killed. If we had just continued and the
13:23
Second World War began twenty years after the end of the First World War, we could extrapolate. If the nuclear weapons hadn't come into existence, we would by this time have had the conflict between the United States and the Soviet Union, capitalism against
13:43
communism with perhaps sixty or eighty million people killed. It's good that we have had this nuclear deterrent, but it has reached an insane size. This development has gone on
14:05
already twenty-five years ago. It had gone far too far. As Professor Philip Morrison at MIT said, we need to reduce the nuclear deterrent from its present completely insane level to
14:22
a somewhat less irrational level. If it were one percent as big as it is now, it would still be a hundred times, involve a hundred times the destructive power of the Second World War. What we need to do is to get it under control to make sure that these nuclear weapons will not
14:45
be used. And of course that means we have to start cooperating. It is really unworthy of the human race, that the nations, great nations of the world should not be
15:04
cooperating with one another and with all the other nations in solving the other great problems that exist in the world of malnutrition, starvation, and the fact that we have a world in which most people are not able to lead good lives. We should, as intelligent beings,
15:27
be working to achieve a world in which every human being has the opportunity to lead a good life. Even with cooperation, it will be difficult enough to solve the great world problems.
15:42
Well, the greatest of all, of course, is militarism. So we need to do something about that. One commentator wrote, you know, President Reagan has said what our policy is. He didn't initiate
16:03
it for 25 years or more. There have been two groups of people in the State Department of the United States, one group saying the time has come when we need to cooperate to solve world problems. The other group has said the United States has twice the wealth, twice the gross
16:24
national product of the Soviet Union. We can stand having a big military budget and the Soviet Union is forced to try to keep up with us. And that means a military burden. This is a much greater one for them. So sooner or later, they will break. One commentator
16:45
wrote to President Reagan's policy of spending 1.6 trillion dollars on militarism over the next five years in order to bankrupt the Soviet Union has already in its first year brought to
17:03
United States to the verge of bankruptcy, not only economically but also spiritually and morally. You know, I believe that human beings are good. I believe in morality. And I deplore
17:23
that the world is being run now in the way that it is being run. I think that it is the duty of every human being to do what he can to eliminate this great evil,
17:44
to do anything that is possible for him to do, to start the world moving in the direction of peace and cooperation and morality. Well, I think one reason for doing this
18:09
is that it will permit human beings to enjoy themselves making quantum mechanical calculations. And I've enjoyed myself over all of the years. Back in 1928, I published a paper
18:28
in the Proceedings of the National Academy of Sciences on the nature of the chemical bond. In it, I said the resonance theory in quantum mechanics shows that the carbon atom
18:45
should form four equivalent bonds directed toward the corners of a regular tetrahedron. And it was only about one sentence, perhaps two, on that subject. It discussed a number of aspects of molecular structure and chemical bond formation. And I think it perhaps ended with
19:05
a statement that detailed account of this work will be published later. Well, three years went by without a detailed account of the work being published. And as I think back two and a half years anyway, as I think back, I think I understand why. The calculations that I had made
19:27
were just so complicated because the radial part of the wave functions for the carbon atom are, they're relatively simple functions, of course, but they're complicated enough
19:41
so that these calculations that I had made, that I had interpreted as showing that the tetrahedral carbon, as providing a theoretical base for the tetrahedral carbon, seemed to me not to be convincing enough to the reader to justify publication.
20:02
They weren't even convincing to me because they were so complicated. So time went by. Now, in I think December of 1930, one day, I had an idea. It's astonishing how hard it is to have ideas, new ideas, but I had this idea. The idea was this. I published back in 1927
20:29
drawings showing the radial distribution of the wave functions in various atoms. And here, the s function, 2s function, and 2p functions of carbon, or the 2p function,
20:42
they are somewhat different functions. 2p, 2s has a node, and the 2p doesn't have a node. But in fact, as you get a little way away from the carbon nucleus, they're pretty much the same. The idea was a very simple one. Why not assume
21:00
that the radial functions are the same for 2s and 2p? And then you just look at the angular functions. Well, the angular function for 2s is just a constant over the surface of a sphere, independent of theta and phi. And the angular function for 2p is just a cosine
21:22
function oriented. There are three of them oriented in three different directions. It's very easy. The mathematics is very easy to handle a constant plus a simple trigonometric function, cosine or sine. So for several hours until early morning the next day, I was
21:44
hard at work. I was hard at work making these simple calculations and getting a whole lot of theories of results, which within three months had been published in a 35-page paper on the
22:02
nature of the chemical bond in the Journal of the American Chemical Society. The first thing that I did was to combine this s function and the p functions into a normalized function and determine the nature of this hybrid function that would give the strongest chemical bond.
22:30
This means it projected to the greatest extent in the direction of the other atom, the hydrogen atom, say, in methane. Having got that function, I asked,
22:44
what's the next best function orthogonal to the first one? And it turned out to be equivalent to the first one and off at the angle of 109.47 degrees. That's just the tetrahedral angle. And you could make a third equivalent function in the fourth one
23:04
so that the s2s function and the 32p functions could be rewritten as four equivalent best bond forming tetrahedral functions directed to our – which were directed, in fact,
23:21
came out from this simple calculation to be directed toward the corners of a regular tetrahedron. So there is the basis of quantum mechanical basis, very simple. It's in the freshman, probably in the high school textbooks of chemistry now, very simple theory of the tetrahedral carbon atom, pretty much the basis of organic
23:47
chemistry. I don't go so far as Dirac went in saying that the Schrodinger equation is the basis of a large part of physics and the whole of chemistry. There's more to chemistry
24:03
than just a calculation of this sort. But it's pretty satisfying to know that this simple theory leads to the explanation of the tetrahedral carbon atom. Well, I'm talking now about bonds formed by the transition metals. How much? 40 years went by
24:33
before I got around to thinking really seriously about bonds formed by the transition metals.
24:42
And perhaps 15 years ago, I suggested to a student working for his Ph.D. degree with me that he tried to find for the transition metals the best hybrid SPD orbitals,
25:01
the best bond orbitals, the best set of nine that you could form, normalized and mutually orthogonal, a pretty difficult problem. And he solved it, and he got his doctor's degree, and I even read his thesis. But it still took me a few years to get really excited about it.
25:24
And then I thought, can't we make progress in understanding the transition metals by using this simple technique of just looking at the wave functions? You have an S function, 4S, say, for the iron group, 5S, 6S for the palladium platinum transition sequences,
25:48
three P functions, and then five D functions, three D functions. And that gives a total of nine. We would expect that transition metals might well be able to form nine single covalent bonds.
26:07
Let me have the slides, and I'll not show those slides anyway, having brought them all the way from California. And if they're here, they'll remind me about what to say next.
26:24
GM Lewis was a Californian, a great chemist who came from Massachusetts Institute of Technology in 1910, I think, to this school in Berkeley that had a few chemists not doing very much.
26:41
And he built up what might well be considered the greatest department of chemistry in the world. In 1916, he wrote a paper on the chemical bond in which he said, the chemical bond is at all times and in all molecules merely a pair of electrons held jointly
27:03
by two atoms. This was essentially the start of modern electronic structural theory of molecules. Langmuir wrote a number of papers in 1919, 1920, 1921, in which he made
27:27
really significant contributions to the electronic structure theory. Next slide, please. Probably few of you have ever seen the picture of GM Lewis.
27:44
I went to Pasadena to be a graduate student in chemistry, physics, and mathematics in 1922. This picture was taken in Pasadena a few years earlier. GM Lewis is the man sitting on the running board of the car. The car belonged to Arthur Amos Noyes, who had been
28:09
at MIT and moved to Pasadena, was the head of the division of chemistry and chemical engineering in California Institute of Technology. He is at the wheel. I went in this car to the desert
28:25
with A.A. Noyes and a couple of others just on an outing a few years later. Next slide. Well, here, there was a discussion going on, an argument about the static atom and the
28:46
dynamic atom. And Lewis said, if we think about the orbit as a whole, a sort of Bohr orbit and not the position of the electron within the orbit, then we may think of each electron
29:01
orbit as having a fixed position in space. The average position of the electron in the orbit may be called the position of the electron, as in the static atom. Well, of course, this is worked out. This is essentially the basis of the calculation.
29:24
Next slide, please, of the calculation that I mentioned. Here is a figure that appeared in my 1931 paper, I think for the first time. Up at the top, we have a sphere. That means that an s orbital has a constant value in the same value in all
29:46
directions. And the p orbitals, the three p orbitals are shown below. They extend farther out in space, but only in certain directions. And John Slater was the first person to say in 1930 that an atom such as sulfur, combining with hydrogen to form hydrogen sulfide,
30:08
should form p bonds, which would be at 90 degrees to one another. The bond angle in H2S is, in fact, 92.5 degrees. And similarly, in arsine, ASH3, and stibian.
30:23
Well, if we combine these functions, the p functions have a positive lobe and a negative lobe, so they add on to s in one direction, subtract from the other, we get—next slide, please—we got a tetrahedral function which has twice the extent of the s orbital in the
30:48
bond direction. And it has a nodal cone at 109.47 degrees, the tetrahedral direction. There's a simple theorem in quantum mechanics that you can form a second best bond orbital
31:05
in the direction in which the first one has a node, has zero value. And this is what leads to the tetrahedral carbon atom. Next slide. And it is the basis of the tetrahedral
31:21
structure of methane. In 1926 and 7, while I was a postdoctoral fellow in Munich with Sommerfeld's Institute for Theoretical Physique, there was a man who got his Ph.D. degree by interpreting the band spectrum of methane to show that the methane molecule is flat,
31:46
a square, the four hydrogen atoms around the carbon at the corners of a square. Well, you know, 1927, science was in a primitive, a very primitive stage. The structure of the molecule wasn't even known. The hydrogen-oxygen distance of 0.965 angstrom, or the bond angle
32:06
of 96 degrees, these things weren't known in 1927. Next slide. And of course, the tetrahedral carbon atom gives a simple explanation of the existence of cis and trans
32:26
disubstituted one, two disubstituted ethylenes. You just assume bent bonds. Two bent single bonds equals a double bond. Three bent single bonds equals a triple bond.
32:42
Very simple. In fact, it even tells the bond length, the carbon-carbon distance. If you assume that the bonds are bent around the arcs of circles, starting out at the tetrahedral angle, then, and have the same, the standard, the normal length,
33:01
1.54 angstrom, then the calculated distance between the carbon atoms agrees within a hundredth of an angstrom for both the double bond and the triple bond with the experimental value. It's a very good representation, very good theory of organic compounds, this chemical bond
33:22
theory. I deplore that students beginning the study of chemistry are taught a lot of complex, largely meaningless material about molecular orbitals. It just confuses them, turns them
33:43
away from chemistry. I'm not saying molecular orbital calculations aren't worth making, but it's pretty poor judgment on the part of textbook writers and teachers to talk about molecular orbitals to beginning students of chemistry. Next slide.
34:07
Well, here's the periodic table. The S and P hybrid orbitals account for a good bit of the chemistry of the short period elements. When we come to the long periods,
34:21
there, each of them involves 18 elements. Argon, then potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, bromine, 18 elements. That's the nine SPD orbitals, each of which
34:40
can be occupied by two electrons with opposed spins. So I'm going to be talking about the transition metals, chromium, manganese, iron, cobalt, nickel, and their heavier congeners. The next slide. Well, in my 1931 paper, there's already a discussion of SPD octahedral orbitals
35:06
and of the square planar orbitals formed by bipositive palladium and platinum and also nickel. They weren't known for nickel yet, but that was a prediction.
35:21
Here we have a slide showing the, on the left side, the ionic view of cobalt hexamine cation, tripositive cation, in which the cobalt atom has a charge of plus three.
35:42
And on the right side is the normal covalent or pure covalent view in which you transfer six electrons to cobalt, so it has a charge of minus three. Well, each of these structures violates a principle that Irving Langmuir proposed 52, 53 years ago,
36:08
the principle of electro neutrality, that in every stable molecule or crystal, the atoms, all of the atoms are electrically neutral or nearly electrically neutral.
36:21
In fact, the bonds here have about, they're covalent bonds with about 50% ionic character. Next slide. Next slide that I seem to have got the same slide in twice. Here we are showing bonds that are 50% covalent and 50% ionic, so that the cobalt atom has zero
36:50
resultant charge. Each nitrogen atom would have a charge of plus one half, except that the nitrogen hydrogen bonds are also partially ionic, so that the nitrogen atoms turn out to be,
37:05
have essentially zero charge. Each hydrogen atom, and there are 18 of those, has a charge of plus one sixth. And of course, in aqueous solution, this charge is partially transferred to the surrounding water molecules, so that the hydrated complex is like a metallic sphere,
37:28
a charged metallic sphere, and that the electric charge is on the surface. Next slide. This diagram shows the Laplace constant, or the…