PhET-Simulations-for-Chemistry/C3/Models-of-Hydrogen-atom/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Models of the hydrogen atom.
00:07	In this tutorial we will, Demonstrate Models of the Hydrogen Atom, PhET simulation.
00:16	Here I am using-Ubuntu Linux OS v 14.04
00:24	Java v 1.7.0
00:29	To follow this tutorial, Learner should be familiar with topics in high school science.
00:37	Using this simulation we will, Visualize different models of the hydrogen atom.
00:44	Explain the experimental predictions of each model.
00:49	Discuss limitations of each model.
00:53	Explain the energy level diagram.
00:56	Determine the orbital shape and orientation from n, l and m values.
01:03	Let us start the demonstration.
01:06	Use the given link to download the simulation.
01:11	I have already downloaded Models of the Hydrogen Atom simulation to my Downloads folder.
01:18	To run the simulation, open the terminal.
01:22	At the prompt type cd space Downloads and press Enter.
01:29	Then type, java space hyphen jar space hydrogen hyphen atom_en.jar and press Enter.
01:41	Models of the Hydrogen Atom simulation opens.
01:45	Top-left corner of the screen has a menu bar with menu items File and Help.
01:52	Below the menu bar, there is a grey button with two options, Experiment and Prediction.
02:01	By default Experiment mode opens.
02:05	On the screen, we see an experimental setup with a light gun to emit beam of photons.
02:13	There is also a Box of Hydrogen.
02:16	This box is filled with hydrogen atoms.
02:20	The zoom-in box represents a single hydrogen atom.
02:25	A message appears.
02:28	It prompts you to click on the red button to turn on the light beam.
02:33	The light gun has two light controls, White and Monochromatic.
02:41	By default White light is selected.
02:45	Click on Prediction option on the grey button.
02:49	Atomic Model panel opens on the left-side of the screen.
02:54	It has a list of Classical and Quantum Atomic Models.
02:59	Here we can check how the prediction of a model matches the experimental results.
03:06	Legend box on the right-side of the screen has a list of sub-atomic particles.
03:13	At the bottom of the screen we have, Slider to control speed of animation Play/Pause and Step buttons.
03:25	The first model of atom proposed, is the Billiard Ball model.
03:30	By default Billiard Ball is selected from the list.
03:35	Billiard Ball Model
03:38	Billiard Ball model is also called as Dalton's atomic model.
03:44	It was proposed by John Dalton.
03:48	According to this model, individual atom is visualized as solid, hard spheres, like billiard balls.
03:58	Click on the red button of the light gun.
04:02	Select White light.
04:05	A beam of photons having different wave lengths pass through box of hydrogen.
04:11	Observe that, All photons in the path of hydrogen atoms are deflected.
04:17	Limitations of Billiard Ball model.
04:21	Here are the limitations of Billiard Ball model.
04:27	Back to the simulation.
04:30	Turn off the light beam.
04:33	Click on Plum Pudding from the Atomic Model list.
04:37	This model was proposed by J. J. Thomson in 1898.
04:43	The positive charge is uniformly distributed and electrons are embedded into it.
04:50	The brown mass is the positive charge.
04:53	Blue color particle in the middle is the electron.
04:57	Click on Show spectrometer check-box.
05:01	Turn on the light beam.
05:04	Select White light.
05:07	When photons strikes electron, the electron moves and photons deflected.
05:13	Notice that, spectrum consists of only emitted uv photons.
05:19	Turn off the light beam.
05:23	Limitations of Plum Pudding model
05:27	Here are the limitations of Plum Pudding model.
05:32	Based on the above observations, Rutherford proposed the Classical solar system model of atom.
05:42	Solar System Model Rutherford nuclear model of an atom is like a small scale solar system.
05:49	Nucleus plays the role of sun and the electrons that of revolving planets.
05:55	The very small positive charge portion of the atom was called nucleus.
06:01	Electrons move around the nucleus.
06:05	They move with very high speed in circular paths called orbits.
06:11	Back to the simulation.
06:14	Pause the simulation.
06:17	Click on Classical Solar System from the list.
06:21	Screen has Show electron energy level diagram check-box at the top-right corner.
06:28	Click on the check box.
06:31	It shows the energy of the electron.
06:35	If this model were true, it should take an electron only a fraction of a second to spiral into the nucleus.
06:43	Turn on the light beam.
06:46	Drag the speed slider to slow.
06:50	Click on Step button to view the energy of the electron.
06:55	Energy of the electron goes from highest to lowest in a fraction of a second.
07:03	We know that this does not happen.
07:07	Atom is known to be stable.
07:10	Turn off the light beam.
07:13	Limitations of Solar System model Rutherford model cannot explain, The stability of an atom and also, The distribution of electrons and their energies.
07:28	Back to the simulation.
07:31	From the Atomic Model list, click on Bohr.
07:35	Neils Bohr proposed a model of hydrogen atom to improve upon Rutherford's model.
07:42	According to this model, The electron moves around the nucleus in an orbit of fixed radius and energy.
07:50	The energy of an electron in the orbit does not change with time.
07:56	These orbits are called energy levels.
08:00	These orbits are represented by n=1,2,3,4 etc in the Electron energy level diagram.
08:13	Turn on the light beam.
08:15	Click on Play button.
08:18	Initially there is an electron in the 1st orbit of an atom.
08:23	Electron energy level diagram shows electron at n =1st level.
08:29	Observe the electronic transition in Electron energy level diagram.
08:34	Electron absorbs photon and gets excited to higher level.
08:39	Energy is emitted when electron moves from higher level to lower level.
08:45	This electron returns back to 1st level.
08:49	Observe the spectrometer.
08:52	Spectrometer shows emitted photons.
08:56	Under Light controls, click on Monochromatic radio button.
09:01	Then check Show absorption wavelengths checkbox.
09:05	You will see four vertical spectral lines.
09:09	These lines represent the wavelengths of absorption.
09:14	The slider is highlighted on the first line.
09:18	Wavelength, 94 nm as shown in the text box.
09:23	As the photon strikes the electron, observe the electronic transition at 94 nm in Electron energy level diagram.
09:32	The electron moves to n= 6th level.
09:36	After a while it moves to lower level by emitting photon.
09:42	Turn off the light beam.
09:45	As an assignment, Select Bohr Atomic model.
09:50	Change the light beam to Monochromatic.
09:53	Observe the electronic transitions at 103 nm, 112 nm, and 122 nm absorption wave lengths.
10:04	Observe the energy level diagram and the spectrometer results.
10:09	Note the observation and give an explanation.
10:13	Limitations of Bohr’s model
10:16	Bohr's model was unable to explain the following phenomena.
10:24	Back to the simulation.
10:26	Another model based on dual behavior of electrons was proposed.
10:32	Click on de Broglie from the Atomic Model list.
10:36	Notice the wave which represents electron in zoom-in box.
10:42	deBroglie Atomic Model: The French physicist, de Broglie in 1924 proposed dual behavior of electrons.
10:51	Like radiation, matter should also exhibit both particle and wavelike properties.
10:58	Electrons should also have momentum as well as wavelength.
11:03	Turn on the light beam.
11:05	Notice that the electron absorbs photon and moves to higher energy level orbit.
11:12	Electron at higher energy level emits energy.
11:16	It returns to the lower energy level orbit.
11:20	Observe the electronic transitions in energy level diagram.
11:25	Top-left corner of the view box has radial view drop-down box.
11:30	Click on drop-down arrow.
11:33	Scroll to 3D view and click on it.
11:37	Now observe the wave nature of electron in 3D view.
11:42	Turn off the light beam.
11:45	In order to explain the spectrum of hydrogen atom, theory of quantum mechanics came into existence.
11:53	Schrödinger Model : Erwin Schrödinger proposed the quantum mechanical model of the atom.
12:00	Schrödinger used mathematical equations to describe the probability of finding an electron.
12:07	Quantum Numbers: The three coordinates that come from Schrodinger's wave equations are quantum numbers, Principal (n), Angular (l), and Magnetic (m).
12:19	Quantum numbers describe size, shape and orientation of the orbitals.
12:26	Back to simulation.
12:29	Click on Schrödinger from the list.
12:32	In the zoom in box, atom is shown with nucleus surrounded by electron cloud.
12:38	Switch back to White light.
12:41	Turn on the light beam.
12:43	Observe that electron absorbs photon and moves to different orbital.
12:49	Observe the shapes of orbitals as the electron moves.
12:54	Notice the electronic transitions in Electron energy level diagram.
12:59	In addition to value of n, energy level diagram has values for l and m also.
13:06	Note n, l, m values at the bottom right corner of the view box.
13:12	Note the change in n, l, m values as the photons strike the electrons.
13:19	All these models compare how the experimental results match with the prediction.
13:26	As an assignment, For the Schrodinger's atomic model, select Monochromatic light beam.
13:34	Note n,l,m values for the electron at four absorption wavelengths.
13:41	Note the orbital shape and possible orientation for each wavelength.
13:47	Let us summarize.
13:49	In this tutorial we have demonstrated, How to use Models of the Hydrogen Atom, PhET simulation.
13:59	Using this simulation we have, Visualized different models of the hydrogen atom.
14:06	Explained the experimental predictions of each model.
14:11	Discussed limitations of each model.
14:15	Determined the orbital shape and orientation from n, l and m values.
14:22	Explained the energy level diagram.
14:25	The video at the following link summarizes the Spoken Tutorial project.
14:30	Please download and watch it.
14:33	The Spoken Tutorial Project team: conducts workshops using spoken tutorials and gives certificates on passing online tests.
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14:46	Please post your timed queries in this forum.
14:51	This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
14:59	Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
15:06	More information on this mission is available at this link.
15:11	This is Meenal Ghoderao from IIT Bombay.
15:15	Thank you for joining.

Contributors and Content Editors

Nancyvarkey