The Plum Pudding Model Is an Atom Model Proposed by JJ Thomson, the Physicist Who Discovered the Electron

Total Page：16

File Type：pdf, Size：1020Kb

The Plum Pudding Model is an atom model proposed by JJ Thomson, the physicist who discovered the electron. It is also known as the Chocolate Chip Cookie or Blueberry Muffin Model. You can easily picture it by imagining the said goodies. For example, you can imagine a plum pudding wherein the pudding itself is positively charged and the plums, dotting the dough, are the negatively charged electrons. Thus, in contrast to today's atom that has a very dense and very small (compared to the whole atom) positively charged nucleus, Thomson's had a more dispersed positive charge. As a whole, the plum pudding representation only strived to explain why most atoms were neutral. It's interesting to note that this model was sometimes visualized as having a cloud of positive charge, a striking contrast to the most recent atomic model which describes the positive nucleus to be surrounded by an electron cloud. The Planetary Model of the atom has an atom consisting of a small, positively- charged nucleus orbited by negatively-charged electrons. Here's a closer look at the Planetary Model, also called the Bohr Model or the Rutherford-Bohr Model. The Bohr Model is a planetary model in which the negatively-charged electrons orbit a small, positively-charged nucleus similar to the planets orbiting the Sun (except that the orbits are not planar). Main Points of the Bohr Model Electrons orbit the nucleus in orbits that have a set size and energy. The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit. Radiation is absorbed or emitted when an electron moves from one orbit to another. Electron Cloud Model As we all know, electrons are found to orbit around the nucleus of an atom. Each orbital in an atom is equivalent to an energy level of the electron. On absorbing a photon (ray of colored light), an electron moves to a higher level of energy. On similar lines, an electron can fall to a lower energy level by emitting a photon (ray of colored light), thus radiating energy. The term, ‘electron cloud’ was used by the Noble Prizewinner Richard Feynman, an American physicist, in The Feynman Lectures on Physics. The model provides the means of visualizing the position of electrons in an atom. What is an electron cloud model? It is a visual model that maps the possible locations of electrons in an atom. The model is used to describe the probable locations of electrons around the nucleus. The electron cloud is also defined as the region where an electron forms a three-dimensional cloud around the nucleus, one that does not move relative to the atomic nucleus. .

Copy Link

Recommended publications

Schrödinger Equation)
Lecture 37 (Schrödinger Equation) Physics 2310-01 Spring 2020 Douglas Fields Reduced Mass • OK, so the Bohr model of the atom gives energy levels: • But, this has one problem – it was developed assuming the acceleration of the electron was given as an object revolving around a fixed point. • In fact, the proton is also free to move. • The acceleration of the electron must then take this into account. • Since we know from Newton’s third law that: • If we want to relate the real acceleration of the electron to the force on the electron, we have to take into account the motion of the proton too. Reduced Mass • So, the relative acceleration of the electron to the proton is just: • Then, the force relation becomes: • And the energy levels become: Reduced Mass • The reduced mass is close to the electron mass, but the 0.0054% difference is measurable in hydrogen and important in the energy levels of muonium (a hydrogen atom with a muon instead of an electron) since the muon mass is 200 times heavier than the electron. • Or, in general: Hydrogen-like atoms • For single electron atoms with more than one proton in the nucleus, we can use the Bohr energy levels with a minor change: e4 → Z2e4. • For instance, for He+ , Uncertainty Revisited • Let’s go back to the wave function for a travelling plane wave: • Notice that we derived an uncertainty relationship between k and x that ended being an uncertainty relation between p and x (since p=ћk): Uncertainty Revisited • Well it turns out that the same relation holds for ω and t, and therefore for E and t: • We see this playing an important role in the lifetime of excited states.
[Show full text]
Modern Physics: Problem Set #5
Physics 320 Fall (12) 2017 Modern Physics: Problem Set #5 The Bohr Model ("This is all nonsense", von Laue on Bohr's model; "It is one of the greatest discoveries", Einstein on the same). 2 4 mek e 1 ⎛ 1 ⎞ hc L = mvr = n! ; E n = – 2 2 ≈ –13.6eV⎜ 2 ⎟ ; λn →m = 2! n ⎝ n ⎠ | E m – E n | Notes: Exam 1 is next Friday (9/29). This exam will cover material in chapters 2 through 4. The exam€ is closed book, closed notes but you may bring in one-half of an 8.5x11" sheet of paper with handwritten notes€ and equations. € Due: Friday Sept. 29 by 6 pm Reading assignment: for Monday, 5.1-5.4 (Wave function for matter & 1D-Schrodinger equation) for Wednesday, 5.5, 5.8 (Particle in a box & Expectation values) Problem assignment: Chapter 4 Problems: 54. Bohr model for hydrogen spectrum (identify the region of the spectrum for each λ) 57. Electron speed in the Bohr model for hydrogen [Result: ke 2 /n!] A1. Rotational Spectra: The figure shows a diatomic molecule with bond- length d rotating about its center of mass. According to quantum theory, the d m ! ! ! € angular momentum ( ) of this system is restricted to a discrete set L = r × p m of values (including zero). Using the Bohr quantization condition (L=n!), determine the following: a) The allowed€ rotational energies of the molecule. [Result: n 2!2 /md 2 ] b) The wavelength of the photon needed to excite the molecule from the n to the n+1 rotational state.
[Show full text]
Bohr Model of Hydrogen
Chapter 3 Bohr model of hydrogen Figure 3.1: Democritus The atomic theory of matter has a long history, in some ways all the way back to the ancient Greeks (Democritus - ca. 400 BCE - suggested that all things are composed of indivisible \atoms"). From what we can observe, atoms have certain properties and behaviors, which can be summarized as follows: Atoms are small, with diameters on the order of 0:1 nm. Atoms are stable, they do not spontaneously break apart into smaller pieces or collapse. Atoms contain negatively charged electrons, but are electrically neutral. Atoms emit and absorb electromagnetic radiation. Any successful model of atoms must be capable of describing these observed properties. 1 (a) Isaac Newton (b) Joseph von Fraunhofer (c) Gustav Robert Kirch- hoff 3.1 Atomic spectra Even though the spectral nature of light is present in a rainbow, it was not until 1666 that Isaac Newton showed that white light from the sun is com- posed of a continuum of colors (frequencies). Newton introduced the term \spectrum" to describe this phenomenon. His method to measure the spec- trum of light consisted of a small aperture to define a point source of light, a lens to collimate this into a beam of light, a glass spectrum to disperse the colors and a screen on which to observe the resulting spectrum. This is indeed quite close to a modern spectrometer! Newton's analysis was the beginning of the science of spectroscopy (the study of the frequency distri- bution of light from different sources). The first observation of the discrete nature of emission and absorption from atomic systems was made by Joseph Fraunhofer in 1814.
[Show full text]
Pioneers of Atomic Theory Darius Bermudez Discoverers of the Atom
Pioneers of Atomic Theory Darius Bermudez Discoverers of the Atom Democritus- Greek Philosopher proposed that if something was divided enough times, eventually the particles would be too small to divide any further. Ex: Identify this Greek philosopher who postulated that if an object was divided enough times, there would eventually be small particles that could not be divided any further. Discoverers of the Atom John Dalton- English chemist who made the “billiard ball” atom model. First to prove that rainfall was a result of temperature change. He was the first scientist after Democritus to build on atomic theory. He also created a law on partial pressures. Common Clues: Partial pressures, pioneer of atomic theory, and temperature change causes rainfall. The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the ﬁle again. If the red x still appears, you may have to delete the image and then insert it again. The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the ﬁle again. If the red x still appears, you may have to delete the image and then insert it again. Discoverers of the Atom J.J. Thomson- English Scientist who discovered electrons through a cathode. Made the “plum pudding model” with Lord Kelvin (Kelvin Scale) which stated that negative charges were spread about a positive charged medium, making atoms neutral. Common Clues: Plum pudding, Electrons had negative charges, disproved by either Rutherford or Mardsen and Geiger The image cannot be displayed.
[Show full text]
Bohr's 1913 Molecular Model Revisited
Bohr’s 1913 molecular model revisited Anatoly A. Svidzinsky*†‡, Marlan O. Scully*†§, and Dudley R. Herschbach¶ *Departments of Chemistry and Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544; †Departments of Physics and Chemical and Electrical Engineering, Texas A&M University, College Station, TX 77843-4242; §Max-Planck-Institut fu¨r Quantenoptik, D-85748 Garching, Germany; and ¶Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138 Contributed by Marlan O. Scully, July 10, 2005 It is generally believed that the old quantum theory, as presented by Niels Bohr in 1913, fails when applied to few electron systems, such as the H2 molecule. Here, we ﬁnd previously undescribed solutions within the Bohr theory that describe the potential energy curve for the lowest singlet and triplet states of H2 about as well as the early wave mechanical treatment of Heitler and London. We also develop an interpolation scheme that substantially improves the agreement with the exact ground-state potential curve of H2 and provides a good description of more complicated molecules such as LiH, Li2, BeH, and He2. Bohr model ͉ chemical bond ͉ molecules he Bohr model (1–3) for a one-electron atom played a major Thistorical role and still offers pedagogical appeal. However, when applied to the simple H2 molecule, the ‘‘old quantum theory’’ proved unsatisfactory (4, 5). Here we show that a simple extension of the original Bohr model describes the potential energy curves E(R) for the lowest singlet and triplet states about Fig. 1. Molecular conﬁgurations as sketched by Niels Bohr; [from an unpub- as well as the first wave mechanical treatment by Heitler and lished manuscript (7), intended as an appendix to his 1913 papers].
[Show full text]
Bohr's Model and Physics of the Atom
CHAPTER 43 BOHR'S MODEL AND PHYSICS OF THE ATOM 43.1 EARLY ATOMIC MODELS Lenard's Suggestion Lenard had noted that cathode rays could pass The idea that all matter is made of very small through materials of small thickness almost indivisible particles is very old. It has taken a long undeviated. If the atoms were solid spheres, most of time, intelligent reasoning and classic experiments to the electrons in the cathode rays would hit them and cover the journey from this idea to the present day would not be able to go ahead in the forward direction. atomic models. Lenard, therefore, suggested in 1903 that the atom We can start our discussion with the mention of must have a lot of empty space in it. He proposed that English scientist Robert Boyle (1627-1691) who the atom is made of electrons and similar tiny particles studied the expansion and compression of air. The fact carrying positive charge. But then, the question was, that air can be compressed or expanded, tells that air why on heating a metal, these tiny positively charged is made of tiny particles with lot of empty space particles were not ejected ? between the particles. When air is compressed, these 1 Rutherford's Model of the Atom particles get closer to each other, reducing the empty space. We mention Robert Boyle here, because, with Thomson's model and Lenard's model, both had him atomism entered a new phase, from mere certain advantages and disadvantages. Thomson's reasoning to experimental observations. The smallest model made the positive charge immovable by unit of an element, which carries all the properties of assuming it-to be spread over the total volume of the the element is called an atom.
[Show full text]
Ab Initio Calculation of Energy Levels for Phosphorus Donors in Silicon
Ab initio calculation of energy levels for phosphorus donors in silicon J. S. Smith,1 A. Budi,2 M. C. Per,3 N. Vogt,1 D. W. Drumm,1, 4 L. C. L. Hollenberg,5 J. H. Cole,1 and S. P. Russo1 1Chemical and Quantum Physics, School of Science, RMIT University, Melbourne VIC 3001, Australia 2Materials Chemistry, Nano-Science Center, Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 København Ø, Denmark 3Data 61 CSIRO, Door 34 Goods Shed, Village Street, Docklands VIC 3008, Australia 4Australian Research Council Centre of Excellence for Nanoscale BioPhotonics, School of Science, RMIT University, Melbourne, VIC 3001, Australia 5Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Parkville, 3010 Victoria, Australia The s manifold energy levels for phosphorus donors in silicon are important input parameters for the design and modelling of electronic devices on the nanoscale. In this paper we calculate these energy levels from first principles using density functional theory. The wavefunction of the donor electron's ground state is found to have a form that is similar to an atomic s orbital, with an effective Bohr radius of 1.8 nm. The corresponding binding energy of this state is found to be 41 meV, which is in good agreement with the currently accepted value of 45.59 meV. We also calculate the energies of the excited 1s(T2) and 1s(E) states, finding them to be 32 and 31 meV respectively. These results constitute the first ab initio confirmation of the s manifold energy levels for phosphorus donors in silicon.
[Show full text]
Niels Bohr and the Atomic Structure
GENERAL ¨ ARTICLE Niels Bohr and the Atomic Structure M Durga Prasad Niels Bohr developed his model of the atomic structure in 1913 that succeeded in explaining the spectral features of hydrogen atom. In the process, he incorporated some non-classical features such as discrete energy levels for the bound electrons, and quantization of their angular momenta. Introduction MDurgaPrasadisa Professor of Chemistry An atom consists of two interacting subsystems. The first sub- at the University of system is the atomic nucleus, consisting of Z protons and A–Z Hyderabad. His research neutrons, where Z and A are the atomic number and atomic weight interests lie in theoretical respectively, of the concerned atom. The electrons that are part of chemistry. the second subsystem occupy (to zeroth order approximation) discrete energy levels, called the orbitals, according to the Aufbau principle with the restriction that no more than two electrons occupy a given orbital. Such paired electrons must have their spins in opposite direction (Pauli’s exclusion principle). The two subsystems interact through Coulomb attraction that binds the electrons to the nucleus. The nucleons in turn are trapped in the nucleus due to strong interactions. The two forces operate on significantly different scales of length and energy. Consequently, there is a clear-cut demarcation between the nuclear processes such as radioactivity or fission, and atomic processes involving the electrons such as optical spectroscopy or chemical reactivity. This picture of the atom was developed in the period between 1890 and 1928 (see the timeline in Box 1). One of the major figures in this development was Niels Bohr, who introduced most of the terminology that is still in use.
[Show full text]
Module P11.3 Schrödinger's Model of the Hydrogen Atom
FLEXIBLE LEARNING APPROACH TO PHYSICS Module P11.3 Schrödinger’s model of the hydrogen atom 1 Opening items 3.4 Ionization and degeneracy 1.1 Module introduction 3.5 Comparison of the Bohr and the Schrödinger 1.2 Fast track questions models of the hydrogen atom 1.3 Ready to study? 3.6 The classical limit 2 The early quantum models for hydrogen 4 Closing items 2.1 Review of the Bohr model 4.1 Module summary 2.2 The wave-like properties of the electron 4.2 Achievements 3 The Schrödinger model for hydrogen 4.3 Exit test 3.1 The potential energy function and the Exit module Schrödinger equation 3.2 Qualitative solutions for wavefunctions1 —1the quantum numbers 3.3 Qualitative solutions of the Schrödinger equation1—1the electron distribution patterns FLAP P11.3 Schrödinger’s model of the hydrogen atom COPYRIGHT © 1998 THE OPEN UNIVERSITY S570 V1.1 1 Opening items 1.1 Module introduction The hydrogen atom is the simplest atom. It has only one electron and the nucleus is a proton. It is therefore not surprising that it has been the test-bed for new theories. In this module, we will look at the attempts that have been made to understand the structure of the hydrogen atom1—1a structure that leads to a typical line spectrum. Nineteenth century physicists, starting with Balmer, had found simple formulae that gave the wavelengths of the observed spectral lines from hydrogen. This was before the discovery of the electron, so no theory could be put forward to explain the simple formulae.
[Show full text]
Lecture #3, Atomic Structure (Rutherford, Bohr Models)
Welcome to 3.091 Lecture 3 September 14, 2009 Atomic Models: Rutherford & Bohr Periodic Table Quiz 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 Name Grade /10 Image by MIT OpenCourseWare. La Lazy Ce college Pr professors Nd never Pm produce Sm sufficiently Eu educated Gd graduates Tb to Dy dramatically Ho help Er executives Tm trim Yb yearly Lu losses. © source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse. La Loony Ce chemistry Pr professor Nd needs Pm partner: Sm seeking cannot be referring Eu educated to 3.091! Gd graduate Tb to must be the “other” Dy develop Ho hazardous chemistry professor Er experiments Tm testing Yb young Lu lab assistants. © source unknown. All rights reserved. This image is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse. 138.9055 920 57 3455 3 6.146 * 1.10 57 5.577 La [Xe]5d16s2 Lanthanum CEase not I to slave, back breaking to tend; PRideless and bootless stoking hearth and fire. No Dream of mine own precious time to spend Pour'ed More to sate your glutt'nous desire.
[Show full text]
Electron Charge Density: a Clue from Quantum Chemistry for Quantum Foundations
Electron Charge Density: A Clue from Quantum Chemistry for Quantum Foundations Charles T. Sebens California Institute of Technology arXiv v.2 June 24, 2021 Forthcoming in Foundations of Physics Abstract Within quantum chemistry, the electron clouds that surround nuclei in atoms and molecules are sometimes treated as clouds of probability and sometimes as clouds of charge. These two roles, tracing back to Schrödingerand Born, are in tension with one another but are not incompatible. Schrödinger'sidea that the nucleus of an atom is surrounded by a spread-out electron charge density is supported by a variety of evidence from quantum chemistry, including two methods that are used to determine atomic and molecular structure: the Hartree-Fock method and density functional theory. Taking this evidence as a clue to the foundations of quantum physics, Schrödinger'selectron charge density can be incorporated into many different interpretations of quantum mechanics (and extensions of such interpretations to quantum field theory). Contents 1 Introduction2 2 Probability Density and Charge Density3 3 Charge Density in Quantum Chemistry9 3.1 The Hartree-Fock Method . 10 arXiv:2105.11988v2 [quant-ph] 24 Jun 2021 3.2 Density Functional Theory . 20 3.3 Further Evidence . 25 4 Charge Density in Quantum Foundations 26 4.1 GRW Theory . 26 4.2 The Many-Worlds Interpretation . 29 4.3 Bohmian Mechanics and Other Particle Interpretations . 31 4.4 Quantum Field Theory . 33 5 Conclusion 35 1 1 Introduction Despite the massive progress that has been made in physics, the composition of the atom remains unsettled. J. J. Thomson [1] famously advocated a \plum pudding" model where electrons are seen as tiny negative charges inside a sphere of uniformly distributed positive charge (like the raisins|once called \plums"|suspended in a plum pudding).
[Show full text]
Cbiescss05.Pdf
Science IX Sample Paper 5 Solved www.rava.org.in CLASS IX (2019-20) SCIENCE (CODE 086) SAMPLE PAPER-5 Time : 3 Hours Maximum Marks : 80 General Instructions : (i) The question paper comprises of three sections-A, B and C. Attempt all the sections. (ii) All questions are compulsory. (iii) Internal choice is given in each sections. (iv) All questions in Section A are one-mark questions comprising MCQ, VSA type and assertion-reason type questions. They are to be answered in one word or in one sentence. (v) All questions in Section B are three-mark, short-answer type questions. These are to be answered in about 50-60 words each. (vi) All questions in Section C are five-mark, long-answer type questions. These are to be answered in about 80-90 words each. (vii) This question paper consists of a total of 30 questions. 4. What is the S.I. unit of momentum ? [1] SECTION -A (a) kgms (b) mskg−1 −1 −1 DIRECTION : For question numbers 1 and 2, two statements (c) kgms (d) kg() ms are given- one labelled Assertion (A) and the other labelled Ans : (c) kgms−1 Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. 5. Which of the following is not a perfectly in elastic collision ? [1] (a) Both A and R are true and R is correct explanation (a) Capture of an electron by proton. of the assertion. (b) Man jumping on to a moving cart. (b) Both A and R are true but R is not the correct explanation of the assertion.
[Show full text]