The History of Atomic Chemistry: Crash Course Chemistry #37

How do you picture an atom in your mind – like
this, or like this, or maybe one of these? If you understand enough about atoms to visualize
any of those things, then you know more about atomic theory than
scientists did just 100 years ago. And, like, WAY more than they thought they
knew 2500 years ago. That’s when Greek philosopher Leucippus and
his pupil Democritus first came up with the idea that matter is
composed of tiny particles. No one knows how they developed this concept, but they didn’t think the particles were particularly special – they just thought that if you cut something
in half enough times, eventually you’ll reach a particle that can’t
be cut anymore. They gave these particles the name “atomos,”
which means uncuttable or indivisible. So basically, they thought that iron was made
up of iron particles and clay was made up of clay particles and
cheese was made up of cheese particles. And they attributed properties of each substance
to the forms of the atoms. So, they thought that iron atoms were hard
and stuck together with hooks, clay atoms were softer and attached by ball
and socket joints that made them flexible, and cheese atoms were squishy and delicious. Now this makes a certain amount of sense if you don’t happen to have access to electron microscopes or cathode-ray tubes or the work of generations
of previous scientists. Because the fact is atomic theory as we know
it today is the product of hundreds, if not thousands,
of different insights. Some models, like that of Leucippus, were
just blind guesses. As time went on, many more were the result
of rigorous experimentation. But, as has been the case in all science, each scientist built on what had been learned before. We’ve been talking a lot about the fine details
of chemistry in recent weeks, and we’re gonna keep doing that as we move on to nuclear chemistry and then to the basics of organic chemistry, but we do, I wanted to set aside some time to explain how we know what we know about the atom today, and how we know that we’re not quite done
figuring it out. [Theme Music] Now you might think that once Leucippus and Democritus came up with the general idea of atoms, it’d be pretty easy for someone else to take
that little, indivisible ball and run with it. But you’d be wrong. The next major developments in atomic theory
didn’t come along for nearly 2300 YEARS. I’ve already told you,
for instance, about the French chemist Antoine Lavoisier,
who proposed the law of conservation of mass, which states that even if matter changes shape
or form, its mass stays the same. And you should remember the English teacher
James Dalton who determined that elements exist as discreet
packets of matter. Thanks to these, and other great minds, by the 1800s we had a better grip on the general behavior of atoms. The next logical question was “Why? Why do
they behave the way they do?” This led to the investigation of atomic structure. In the 1870s, scientists began probing what
stuff was made of using discharge tubes, basically gas-filled tubes with electrodes
in each end, which emit light when an electrical current passes through them – basically, what a neon light is. Because this light was originally produced
by a negative electrode, or cathode, it was called a cathode ray,
and it had a negative charge. But in 1886, German physicist Eugen Goldstein found that the tubes also emitted light from the positive electrode, basically, a ray headed in the opposite direction, which meant that there must also be a positive charge in matter. Goldstein didn’t fully understand what he’d
discovered here – I mean, scientists still hadn’t figured out what was responsible for the negative charge in the rays either. Then, English physicist J.J. Thompson took
the discharge tube research further: by measuring how much heat the cathode rays
generated, how much they could be bent by magnets and
other things, he was able to estimate the mass of the rays. And the mass was about 1000 times lighter than a hydrogen, the smallest bit of matter known at the time. He concluded that the cathode “rays” weren’t
rays or waves at all, but were, in fact, very light, very small
negatively-charged particles. He called them “corpuscles;” we call them
“electrons.” So even though we didn’t understand what shapes
they took, we knew that there were both negative and
positive components to matter. The next question was “How were they arranged
in the atom?” Thompson knew that the atom overall had a
neutral charge, so he imagined that the negatively charged electrons must be distributed randomly in a positively charged matrix. And the very English Thompson visualized this
model as a familiar English dessert: plum pudding, the positive matrix being the cake, and the electrons the random, floating bits of fruit within it. Even today, Thompson’s model of the atom continues
to be called the “plum pudding model.” And while a single electron’s motion is random,
the overall distribution of them is not. The next big step was taken by New Zealander
Ernest Rutherford in 1909. He designed an experiment using an extremely thin sheet of gold foil and a screen coated with zinc sulfide. He bombarded the sheet with alpha particles,
which he didn’t really know what they were, just that they were produced by the decay of radium, they were positive charged, and they were really, really small. He expected them to just fly right through the foil, with no deflection, and many of them did just that. But as it turned out, some of the particles were deflected at large angles and sometimes almost straight backward. The only explanation for this was that the
entire positive charge of an atom, the charge that would repel an alpha particle, must be concentrated in a very small area,
an area that he called “the nucleus.” Because most of the alpha particles passed
right through the atoms undeterred, Rutherford concluded that most of the atom
is empty space, and he was correct. Rutherford would later discover that if he
bombarded nitrogen with alpha particles, it created a bunch of hydrogen ions. Now he correctly surmised that these tiny positively charged ions were themselves fundamental particles: Protons.
Now we’re getting close to reality. So these chemists had a fairly good idea of
the structure of the atom, they just needed to figure out what exactly
the electrons were doing. Enter Niels Bohr. In 1911, the same year the results of Rutherford’s
gold foil experiment were published, Bohr traveled to England to study with Rutherford. And as a physicist, he was also interested
in the mathematical model set forth by German physicists Max Planck and Albert Einstein to explain the behavior of electromagnetic energy. Over time, Bohr came to realize these mathematical principles could be applied to Rutherford’s atomic model. His analysis of the gold foil experiment and
calculations based on the proportion of the alpha particles
that went straight through, those that were slightly deflected, and those
that bounced almost completely backward, allowed him to predict the most likely positions
of electrons within the atom. Bohr’s resulting model, sometimes called the planetary model, is still familiar to most people, probably including you. It represents the electrons in orbits around
a small central nucleus. Each orbit can have a specific number of electrons, which correlates to the energy levels and
orbitals in the modern model of an atom. And while it’s definitely flawed, Bohr’s model is very close to reality in some important ways. But like everyone I’ve mentioned in the past couple of minutes, Bohr was at once fantastically right and way off. The problem was those pesky electrons. It was the German theoretical physicist Werner
Heisenberg who got everyone to understand just how huge
and mind-blowing this electron problem was. But he was also the one who helped tie the
whole mess up into a neat little bundle. Using his wicked math chops, Heisenberg discovered
that it is impossible to know with certainty both the momentum of an electron or any subatomic
particle and its exact position. And the more you know about one of those two variables, the harder it gets to measure the other one. So if you can’t measure the position or momentum
of an electron, you obviously can’t say with certainty that the electrons in an atom are all neatly aligned in circular orbits. So he and a new wave of physicists and chemists
proposed a new theory: a quantum theory, which proposes that electrons weren’t particles or waves, instead, they had properties of both and neither. By this thinking, the arrangement of electrons around a nucleus could only be described in terms of probability. In other words, there are certain regions where an electron is much more likely to be found. We call these regions “orbitals.” You know, the very same orbital that you and
I have been talking about – the ones that go by the names “s and d and
p and f” and that form sigma and pi bonds – those are the things that Heisenberg’s theory
predicts. And that’s the modern understanding of atoms. Because it’s based on probability, quantum
atoms are often drawn as clouds with the intensity of color representing
not individual electrons but the probability of finding an electron
in any particular position. For this reason, the quantum model is often
called the cloud model of the atom. And now ya know! All the people I’ve mentioned and many others put their heads together over time to build this current and – I might say – quite elegant understanding
of atomic theory. Now, after 2500 years, even though we can’t see them, we can know what they’re like and how they work, because a long succession of scientists contributed
bits and pieces to the whole fantastic picture. But it’s also important to recognize that
we still may not be quite all the way right. Thompson’s contemporaries were sure that the
plum pudding model was right; scientists in Bohr’s day fully believed that
the planetary model was right, and today we’re extremely confident that the
quantum model is correct. But it may not be all the way correct, and
that’s where you come in: the only way we can go on being sure is to
keep asking questions and conducting experiments. And that’s why you’re taking chemistry
and physics. Pay attention! Thank you for watching this episode of Crash
Course Chemistry. If you paid attention, you learned that Leucippus
and Democritus originated the idea of atoms nearly 2500 years
ago, but that the real work didn’t really begin
until both protons and electrons were discovered
by experimenting with discharge tubes, and how Ernest Rutherford figured out what
and where the nucleus is. You also learned that chemistry can sometimes
be done with just math, like how Bohr figured out his model or the way that Heisenberg used math to usher
in the quantum theory of the atom. This episode written by Edi Gonzales and edited
by Blake de Pastino. Our chemistry consultant is Dr. Heiko Langner, and it was filmed, edited and directed by Nicholas Jenkins. The script supervisor was Katherine Green,
Michael Aranda is our sound designer, and Thought Cafe is our graphics team.

Comments 98

  • Wait, I thought fundamental particles were particles like leptons and quarks. Particles that are in their most simplest form.

  • Wait, I thought fundamental particles were particles like leptons and quarks. Particles that are in their most simplest form.

  • my bearded dragon bit the subscribe button so now im subscribed

  • What about Schrödinger??

  • 2:19 sec he said John Dalton as James Dalton XC took me soo long to find out :(. It's one of my chemistry notes.

  • yo y am I taking phy and chem?!

  • Anyone else here because of a Science professor / teacher?

  • 2:20 You mean john?

  • i love the awkwardness his voice carries when he says "We need you."

  • Maybe "cloud" computing is a parody of "quantum" computing…

  • 2:16
    You said James, but the screen says John.

  • Um actually . There are two seperate thomsons . William thomson came up with the plum pudding module

  • Why are all the scientists soooooooooooooooooo colorful in the vid?

  • You spoke fast.

  • Did anyone notice his save ginny t shirt ?
    All Potter head like

  • well this bohrs me alot

  • y i needed to reduce the speed to 75 to understand what ur saying but thx.

    Good job.

    at least i can understand now what you're saying

  • Why can't you grow a beard?

  • 2:17 James Dalton ☺☺😊

  • Cramming for this damn Chem midterm.

  • Very well done sir

  • Nd what about maharshi kanad sir india…?

  • Hey bill Gaichas

  • 4:24 rutherford worked with eugene goldstein so basically the gold-foil experiment was basically a collaboration

  • 1:33 HOw we know WHAT we know


  • omg yesssssss

  • I am the one who knocks….

    Is that a Witch&Wizard reference????

  • Who really proposed the planetary model? My teacher said it was rutherford. Ive searched and searched for answers, I saw websites saying that it was rutherford and some saying it was bohr. Im confused, anyone please help.

  • Paradoxes of atomism

    If it were possible to continue the division of matter indefinitely, I would have thought it more probable that this process could be carried out to infinity (thesis of infinite divisibility, contrary to atomistic antithesis).

    The problem is that we can not and do not have the colossal force to do this, because we are physically limited, we can only at most split up to a few fractions of sand, because we can not get the pieces too small to be divided again and so on , only the cosmic forces of the universe could make or a God out of infinite power.

    It results in unsustainable paradoxes and absurdities to defend the thesis of the existence of indivisible material entities / elements, the atoms, as they considered Democritus and Leucippus, a thesis that Aristotle correctly rejected.

    Why do we have to accept the existence of atoms if experience shows us that all compound bodies are divisible indefinitely to our last tactile-sensitive limits?

    If all the material elements are breakable into smaller parts, from the softest to the hardest, an iron bar when we hit it kneads and looses small pieces of metal and sparks of fire – energy, revealing its divisibility to us, why then do we have to to accept that atoms (indivisible fragments of matter) exist?

    This atomistic thesis leads us to the paradox well demonstrated by Anaxagoras and Aristotle, that the parts are greater than the sum of the whole, for the components of the self are indivisible and not eternal. The results are the only and most perfect to be realized in all corpus of corruptible and mortal, which results in the refutation of atomism by reduction to the absurd.

    Another paradox reveals itself is not a fact of existing atoms but is not necessarily indivisible, it is not necessary to prepare an atom for its existence, for who can be indivisible, the ultimate of existence, eternal, indestructible, immune to all sorts of shocks and destructions. Existing and eternal exist, to probe and to separate the various clusters in concentrated points without space, resulting in an inexistence of cohesion / physical concretion and consequent non-existence of visualizing the bodies and material bodies! In what results in a further logical – qualitative refutation of atomism, by a new reduction to the absurd.

    And finally, indivisible and eternal atoms unite with other equally indivisible and eternal atoms, through connections made of finite and divisible matter as is our physical – corporeal composition and that of all the animate and inanimate bodies of the world, is an absurd total in this thesis, for where would arise a divisible and finite matter that binds atoms, if these same atoms are all indivisible, eternal and indestructible particles? Of the very primordial atoms that gave birth to the whole universe? But would a finite and divisible matter arising from indivisible and eternal atoms not be an unacceptable corruption of the eternal and indivisible essence of atoms? An indivisible atom that gives rise to a divisible matter would not have to possess the germ of divisibility in its essence, revealing in the truth that it is no atom, but a corruptible and perfectly divisible matter, which would refute the very Democritean thesis of existence of atoms?

    Do you perceive so much of metaphysical absurdities, paradoxes, and idiosyncrasies that the theory of atoms has borne since over 2600 years ago?

    In the antithesis to the atomist theory, we can not observe and test the process of division ad infinitum, because obviously we have spatial and physical – temporal limits, but at least it is indirectly based on ordinary experience, being a much more rational and scientific hypothesis than considering the hypothesis of finite divisibility in final and eternal atoms, for we have no example of phenomenon or object observable in experience that is indivisible, indestructible, incorruptible, and eternal, whereas for the philosophical hypothesis of indefinite or infinite divisibility we have the support of a sensory experience that all objects, bodies and physical phenomena are divisible or decomposable into smaller, corruptible and destructible parts!

  • Why would Rutherford choose radium? Where did he get radium in his time?

  • You talk so fast like rapping, not all people are english people, we slowly analyzing your thoughts so then we have to adjust😁haha but thanks for your informations.

  • We were doing this in class and had to write down stuff now I’m here

  • Copy and paste my name: H. Tomasz Grzybowski in Google, get to the Research Gate page or to Academia page and find my article "Compressible Droplet Atom Structure Theory".

  • how about james chadwick?

  • Mind: UNLOCKED

  • I need this dude as my chem teacher, I'll be getting grades higher than Jin's confidence in his looks

  • Dude….slow down

  • so who discovered neutrons

  • 0:23 They developed it with the Pythagorean Theorem, Zeno's paradox and the Golden Ratio 😂😂😂
    (A reference to AC Odyssey)

  • What’s up future generations of the world

  • In the end you spell Heisenberg as Heisenburg.

  • Sooo… Didnt feel like including how/when neutrons were discovered? Yeah, those things arent that important. Youre right!


  • the videos from 2006 are helping dude

  • How are ya doing, people doing homework?

  • Operation chungus is a go☎️


  • Crash course Narrator: "The english teacher James Dalton"

    Random Guy: Its not James Dalton, Its John Dalton!

    Who the hell needs a script if you already done it😃

  • Albert Einstein Has Left The Chat

  • So who discovered the neutrons???

  • I like you videos. Thank you so much. I prescribe you to make your videos in simple words and slow tempo so that everyone can understand in a manner through an skematic representation. What is the difference between ELEMENT & COMPOUND? Love bro.

  • how do you form an atom in your mind like this or this or maybe one of these. If you understand enough about atoms to visualize any of these things. Then you know more about atomic care than scientists did 100 years ago. and as seen more than they thought they knew 2500 years ago. it is then Greek philosopher leucippus and his student democracy. First came the idea that matter consists of small particles. no one knows how they developed this concept but they did not believe that the particle was particularly special. they just thought that if you cot something in half enough times. Possibly you will reach a particle that cannot be cut anymore. they gave these particles the name atoms which means invaluable or indivisible. so basically they thought iron was made of iron particles. and clay consisted of clay particles and cheese consisted of soot particles. and they attributed the properties of each substance to the forms of the atoms. so they thought iron atoms were difficult and fished with hooks. Clay atoms were softer and attached to ball and sleeve joints that made flexible. and the cheese atoms were squishy and delicious. Now gives some meaning if you do not happen to have access to electron microscope. or cathode ray tubes or the work of generations of former researchers. since fact is atomic theory that we know today is hundreds of products. if not thousands of different insights. some models like that for leucippus were just blind guesses. As time passed many more were the result of strict experimentation. But as has been the case in all science, every scientist built on what has been learned before. We have talked a lot about the fine details of chemistry in recent weeks. and we will continue to do so when we move on to nuclear chemistry and then to the basics of organic chemistry. But we did, I wanted to spend some time explaining how we know what we know about the atom today. and how we know we are not completely ready to figure it out. Now you may think that once leucippus and democracy came up with the general idea of ​​atoms. It will be quite easy for someone else to take that little one. indivisible ball and run with it. But you will go wrong.

  • Thank you!

  • hi thanks for your lessons….they r very helpful

  • raise your hand if you're cramming for a test you forgot about

  • Test tomorrow. Time to binge watch these.

  • Who’s here for THSS science 8

  • loona really brought me here huh,,, im in too deep 🤪

  • Save Ginny !!

  • Pause at 5:25

  • this is way more simple and quick than the vid we were assigned to watch

  • Cheese particles ah…….

  • Correction: Indian philosopher kannad first theorised it not Democritus

  • Thank you for the explanation, i had to put you in 0.75 speed tho hahahaha.

  • 5:23 actually still we are so far from reality!

  • Sir why did bohrs theory went wrong

  • Is it James or John Dalton?

  • I’m using this for a project just so you know & don’t sue me thx

  • The information is correct but I'd recommend using the tool setting to play back at .75 or .5 speed and also look away from the screen. The rapid speech and constantly shifting video scenes made this difficult for me to process -even though my undergrad was in physics. I guess in 2013 this was the style of creating videos.

  • 2:16 it's John not James


  • 3:13 JJ Thomson, not Abrahams

  • John or James Dalton?

  • you said JAMES Dalton.

  • In the Rutherford experiment, he didn't expect the alpha particles to go straight through. They were positive and so was the atom's emitted charge which means he expected them to repel. Them going straight through showed that there was a lot of empty space.

  • they came up with a theory, A QUANTUM THEORY!!

  • My Physicochemistry teacher (even though she and everyone in my school speak Spanish) recommended us your channel, and my God! I understood everything! Thank you very very VERY much to all of you for taking the time to share your knowledge with us!

  • Interesting facts=
    1. You can drink lava once.
    2. 0.99999 = 1
    3. We know 0.1% of everything, we think
    4. Apple did not fall on newton. It fell next to him.
    5. This is a comment.

  • 390 dislikes = J J Thompson's great great great grandchildren

  • What about rishi kannad

  • How can you compare the atomists ideas to our current scientific knowledge of the atom?

  • What about vector atom model??

  • I love Hank Green.

  • So fast in speaking! I didnt understand what he say

  • This video is great but you speak very quick

  • he's wearing a harry potter shirt :))))

  • God created atoms.

  • Can someone olz provide me a picture of cloud model atom woth the orbitals included in them please

  • Is James Dalton other name of John Dalton..,….

  • Actually the INDIAN PHILOSOPHER MAHARISHI KANAD gave the idea of ATOM as ANU…….but some BRITISH ASSHOLES said that its WTF

  • I have a chemistry test tomorrow and this is my substitute for studying

  • baka naman😂

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