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Atomic Theory History

Added Sep 22, 2015 •

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how do you picture and out of in your mind like this like this or maybe one of these if you understand enough about how to visualize any of those things than you know more about atomic play The Scientist did just a hundred years ago and like way more than they thought they knew 2,500 years ago and his pupil put the idea that matter is composed of tiny particles no one else that they didn't think the particles were particularly eventually you'll reach a particle that can't be cut anymore they gave these particles the name a Tomos which means uncuttable or indivisible Kohl's in clay was made up of clay particles and cheese was made up of cheese particles tributed properties of each substance to the forms of the atom so they thought that another with hooks play atoms were softer and attached by a ball-and-socket joints that made them flexible and cheese Adams were squishy and delicious makes a certain amount of sense if you don't have it turn access to electron microscopes are cathode ray tubes are the work of generations of previous scientists  today is the product of hundreds if not thousands different Insight some models like that of Lupus were just blind guesses as time went on many more were the result of rigorous experimentation all science each scientists built on what have been learned before and then to the basics of organic chemistry but before 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 done figuring it out I am I think that once Lucy passing Democritus came up with the general idea of atoms and be pretty easy for someone else to take that little indivisible ball and run with it when you be wrong law of conservation of mass which states that he lives 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 discrete what's the 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 behave the way they do this led to the investigation of atomic structure in 1870 scientists began probing what stuff was made of using discharge tubes basically gas-filled rooms with electrodes in each end which emits light when an electrical current passes through them basically what in the on light is it go this light was originally produced by a negative electrode or I thought it was called a cathode-ray and it had a negative charge 1886 German physicist Oregon Lisa Ray heading in the opposite direction which meant that there must also be a positive charge in matter ghost didn't fully understand what he discovered here I mean scientist still had figured out what was responsible for the negative charge in the Rays either English charge how much do they can be bent by magnets and other things he was able to estimate the mass of the Rays and the mass was about a thousand times lighter than the smallest bit of matter known at the time he concluded that the cathode rays or waves at all but were in fact very light very negatively charged particles electrons play dominance the matter the next question was how were they arranged in the atom overall had a neutral charge must be distributed randomly in a positively charged Matrix and the electrons do random floating bits of fruit within a Thomson's model of the atom continues to be called The Plum Pudding model world distribution of them is not next big step was taken by New Zealander Ernest Rutherford in 1909 he designed experiment using an extremely thin sheet of gold foil and the screen code with the zinc sulfide in the foil with Alpha Barnacles which you didn't really know what they were just that they were produced by the decay of radium we really really small and many of them did just that some of the particles were deflected singles in sometimes straight backward only explanation for this was that the entire positive charge in an atom the charge that would repeal an alpha particle must be concentrated small area an area that he called the nucleus because most of the alpha particles pass right through the atoms undeterred Rutherford concluded that most of the atom is empty space and he was correct Rutherford would later discovered that if he bombarded nitrogen without the particles it created a bunch of hydrogen ions now he correctly surmised that these tiny positively Scions wear themselves fundamental particles protons now we're getting close to reality so these good idea of the structure of the atom exactly the electrons were doing Enter Niels Bohr in 1911 the same year the results of Rutherford's gold foil experiment were published boar traveled to England to study with does a physicist he was also interested in the mathematical model set forth by German physicist Max Planck energy not the bees mathematical principles can be applied to Rutherford's atomic model what's the bounce almost completely backward allowed him to predict the most likely positions of electrons within the atom voraz resulting model sometimes called the planetary model is still tell me all year to most people probably including you it represents the electrons in orbit around a small Central nucleus each orbit can have a specific number of electrons correlates to the energy levels and orbitals in the modern model of an atom in the past couple of minutes more was at once fantastically right and way off problem of those pesky electrons Heisenberg who got everyone to understand just how huge and mind-blowing is electron problem was it was also the one who helped out a little bundle jobs 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 variables the harder it gets to measure the other one so if you can't measure the position or momentum of an electron there are a bit so he and a new wave of physicists and chemists proposed a new theory of quantum theory which proposes that electrons were part acles or waves instead 10 properties of both and neither by this thinking the arrangement of electrons around the nucleus could only be described in terms of probability likely to be found and that form Sigma and Pi bonds are the things that Heisenberg's theory predicts and that's the modern understanding of atom because it's based on probability Quantum style atoms are often drawn is foods with the intensity of color representing not individual electrons but the probability particular position I know you know other people have mentioned and many others put their heads together over time to build this current and I might say quite elegant understanding of atomic theory after 2500 years even though we can't see them we can know what they're like it how they work because a long succession of scientists contributing bits and pieces to the whole fan plastic picture of the we still may not be quite all the way right I fully believe that the planetary model was riding today we're extremely confident that the quantum model is correct but it may not be all the way corrected where you come in the only way we can go on being sure if they keep asking questions in conducting experiments that's why you're taking chemistry and physics should thank you for watching this episode of Crash Course chemistry if you paid attention you learn that new simplest and Democritus originated the idea of atoms nearly 2,500 years ago but the real work didn't really begin both protons and electrons were discovered by experimenting with discharge tubes and how Ernest Rutherford figure it out what and where the nucleus is you also are in the chemistry what has be done with just Matt like how Bohr figured out his model or the way that Heisenberg use map to usher in the quantum theory of the atom buy Blakeney pass Dino our chemistry consultant is dr. haikal langner and it was filmed edited and directed by Nicholas Jenkins the script supervisor was Catherine green Michael Ronda is our sound designer call Cafe is our Graphics team

Uploaded by Laura Houston.

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Atomic Theory History

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