Videos

Atomic Theory: The History of Atomic Chemistry - Crash Course Chemistry

Added Sep 20, 2016 •

Copy this URL:
Embed code:	<iframe class="edlio-embed-player" type="text/html" width="640" height="360" src="//bhs.bartlettschools.org/apps/embed/?v=121050" frameborder="0" allowfullscreen></iframe> Change dimensions

Show Transcript

how do you picture and out of in your mind like this like this or maybe one of these if you understand enough about have to visualize any of those things than you know more about atomic then the scientists did just a hundred years ago and like way more than they thought they knew 2,500 years ago put the idea that matter is composed of tiny particles known about this concept they didn't think the particles were particularly special 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 close and play with made up of clay particles in Jesus was made up of cheese particles and they attributed properties of each substance to the forms of the atoms so they thought that together with hooks Clay Adams we're 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 Max has two electron microscopes are cathode ray tubes are the work of generations of previous scientists different Insight some models like that of Lucifer's 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 pass in 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 didn't come along for New Year's law of conservation of mass which states that has 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 types of matter thanks to these and other great minds by the 18 hundreds 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 phones with electrodes in each end which emits light when an electrical current passes through them basically what a neon light as it was originally produced by a negative electrode or load it was called a cathode-ray and it had a negative charge in 1886 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 Aladdin make it out what was responsible for the negative charge in the Rays either then English charge how much 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 hide the smallest bit of matter known at the time he concluded that the cathode rays Rays or waves at all but were in fact very light very negatively charged particles we call them electrons understand what they were both negative tell an instant matter the next question was how were they arranged in the atom overall had a neutral charge so he imagined that the negatively charged electrons must be distributed randomly in a positively charged Matrix English and the electrons do random floating bits of fruit with Anna today Thomson's model of the atom continues to be called The Plum Pudding model of single electrons 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 go to zinc sulfide in the foil with alpha particles which you didn't really know what they were just that they were produced by the decay of radium really really small X Factor this fly right through the phone with no deflection and many of them did just that but as it turned out some of the particles were deflected at Large and sometimes straight backward the 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 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 Scion 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 he was also interested in the mathematical model set forth by German physicist Max Planck matheny's mathematical principles can be applied to Rutherford's atomic model the bounce almost completely backward allowed him to predict the most likely positions of electrons within the atom for his resulting model sometimes called the planetary model the still tell me what 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 important 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 the whole mess up a little bundle 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 and electron complete to be found these regions orbitals turn that form Sigma and Pi bonds those are the things that Heisenberg's theory predicts and that's the modern understanding of atoms based on probability dogs with the intensity of color representing not individual electrons but the probability of finding an electron in any particular position for the quantum model is often called Adam I know you know all the 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 science is contributing bits and pieces to the whole fan plastic picture of the we still may not be quite all the way right can't fully believe 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 do 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 the new tsipis and Democritus originated the idea of atoms nearly 2,500 years ago but the real work didn't really beginning both protons and electrons were discovered by experimenting with discharge tubes and how Earnest Rutherford figured out what and where the nucleus is also on the chemistry what must be done with just math 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 Pasadena 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 what Cafe is our Graphics team

Uploaded by Laura Houston.

Videos

Atomic Theory: The History of Atomic Chemistry - Crash Course Chemistry

More videos from Laura Houston