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Chapter 7
Atomic Structure
7.1
Title
 Electric discharge in an evacuated tube
Caption
 In 1838, Michael Faraday studied electric currents with an apparatus like this one. The invisible carrieers of the current from the cathode to anode in these empty tube were called cathode rays.
Keywords
 cathode ray, electron, atomic structure, cathode, anode
7.3
Title
 Cathode ray experimental apparatus
Caption
 Thomson's apparatus for determining the mass to charge ratio, me/e. of cathode rays utilized a cathode ray tube in which the anode had a slit that allowed the "ray" to pass through. The electrons in the ray were then moved by magnetic fields and electrically charged plates. Thomson balanced the deflection by the magnetic field and the electrical plates to cancel out, as shown by a net lack of deflection (all shown by the red arrows.) The ratio of the elctric field strength to magnetic field strength needed to exactly balance gave the charge to mass ratio.
Keywords
 atomic structure, Thomson, cathode ray, electron
7.4
Title
 Millikan's oil-drop experiment
Caption
 Oil droplets from an atomizer enter the apparatus through a tiny hole. Some droplets acquire a frictional electric charge as they escape from the atomizer. A source of ionizing radiation, such as X rays, also produces ions. The absorption of these ions sporadically changes the electric charges on the droplets. The droplets are observed through a telescope with a measuring scale in the eyepiece.
Keywords
 Millikan, electron, oil drop, charge, atomic structure
7.5
Title
 Thomson's "raisin pudding" model of atom
Caption
 For a helium atom, the model proposes a large spherical cloud with two units of positive charge. The two electrons lie on a line through the center of the cloud. The loss of one electron produces the He+1 ion, with the remaining electron at the center of the cloud. The loss of a second electron produces He+2 , in which there is just a cloud of positive charge.
Keywords
 Thomson, "raisin pudding" , "plum pudding", atom, model, atomic structure
7.6
Title
 Rutherford's Experiment
Caption
 Much to his surprise, Rutherford observed that most alpha particles (essentially, a helium nucleus) shot at a piece of thin gold foil passed through the foil with little change in trajectory. A small number were scattered at large angles. The bottom figure shows the model of the atom that developed from this experiment, that most of the atom's volume is empty space with a dense positively charged nucleus.
Keywords
 Rutherford, gold foil, nucleus, atomic structure
7.7
Title
 Mass spectrometer
Caption
 A gaseous sample is ionized by bombarding it with electrons in the lower part of the apparatus (not shown), producing positive ions. The ions pass through an electric field in which they are brought to a particular velocity. The ions then pass through a narrow slit into a curved chamber. A magnetic field is applied perpendicular to the beam of ions (perpendicular to the page). All the ions with the same mass-to-charge ratio are deflected into the same circular path. (In most cases, the ionic charge is 1+ and the mass-to-charge ratio is the same as the mass.) Modern spectrometers use electronic detection devices rather than photographic plates or film to establish mass-to-charge ratios and relative numbers of ions.
Keywords
 mass spectrometer, charge to mass ratio
7.8
Title
 Mass spectrum for Mercury
Caption
 The photographic record of Figure 7.7 has been converted to a scale of relative numbers of atoms. The percent natural abundances for the mercury isotopes are: 196Hg, 0.146%; 198Hg, 10.02%; 199Hg, 16.84%; 200Hg, 23.13%; 201Hg, 13.22%; 202Hg, 29.80%; 204Hg, 6.85%.
Keywords
 mass spectrometer, isotope, mercury, abundance, graph
7.9
Title
 Simplest wave motion: traveling wave in a rope
Caption
 Imagine an infinitely long rope. Up-and-down hand motion (top to bottom) causes waves to pass along the rope from left to right. The up-and-down motion of a typical point (dot) on the rope is also shown. This one-directional moving wave is called a traveling wave.
Keywords
 wave, electron, atomic structure, electromagnetic spectrum
7.10ab
Title
 Electromagnetic wave
Caption
 This artists rendering visualizes an electromagnetic wave as a superposition of two wave motions, that of an alternating electric field and, perpendicular to it, an alternating magnetic field. These alternating fields are generated by the relative motion of electric charges. To travel the same distance requires four cycles of the wave in (b) and only two cycles of the wave in (a). The wave in (b) has a higher frequency and a shorter wavelength, l, than the wave in (a). The wave in (a) is shown with a greater amplitude (intensity) than in (b), but the amplitude of a wave is independent of frequency and wavelength.
Keywords
 electromagnetic, waves, spectrum, frequency, wavelength, magnetic
7.11
Title
 Electromagnetic spectrum
Caption
 The visible region of the electromagnetic spectrum, which extends from red at the longest wavelength to violet at the shortest wavelength, is only a small portion of the entire spectrum. The approximate wavelength, frequency ranges, and uses of some other forms of electromagnetic radiation are also indicated.
Keywords
 electromagnetic wave, visible, light, wavelength, frequency
7.12
Title
 Spectrum of ordinary white light
Caption
 Red light is bent the least and violet light the most when white light is passed through a glass prism. The other colors of the visible spectrum are found between red and violet.
Keywords
 prism, light, rainbow, spectrum, wave
7.13
Title
 Visible spectrum of hydrogen
Caption
 The visible spectrum of hydrogen consists of only 4 bands of light at particular wavelengths. This spectrum is generated when (a) gaseous H2 is excited by an electrical current and (b) the light given off by the gas is split by a prism.
Keywords
 line spectrum, hydrogen, neon
7.14
Title
 Line spectra of selected elements
Caption
 Atomic spectra of several elements are shown here. Wavelengths are given in angstrom units (1 =10-10 m). Each element has its own distinctive spectrum which can be used to identify the element. In addition to their practical use in analyzing matter, atomic spectra have led to many of the ideas concerning atomic structure.
Keywords
 line spectra, wavelength, atomic structure
7.15
Title
 The emission spectrum of helium.
Caption
 An emission spectrum of helium can be generated by running an electric current through gaseous helium. The light that is produced can be split by a prism into its single wavelengths, as show in the bar on the left. The emission spectrum of helium consists of six colored lines in the visible portion of the electromagnetic spectrum. The quantity of the elemtn is determined from the intensities of the lines; the more intense the line, the greater the amount of the element.
Keywords
 line spectra, prism, emission, helium
7.17
Title
 Photoelectric effect & the frequnecy of light
Caption
 A beam of white light is dispersed into its wavelength components by a quartz prism and falls on a metal sample (potassium, in this case). Light of the highest frequencies (violet and ultraviolet) produces the most energetic photoelectrons (longest arrows). Light of lower frequencies (for example, orange) results in less energetic photoelectrons (shorter arrows). Light with a frequency lower than 4.23*1014 s-1 (710 nm) produces no photoelectric effect at all on potassium, regardless of how bright (intense) the light is.
Keywords
 photoelectic effect, plank, photon, light, energy, frequency.
7.19
Title
 Model of hydrogen & emission spectrum
Caption
 A portion of the hydrogen atom model is shown with the nucleus at the center of the atom and with the electron in one of a set of discrete orbits n=1, 2, 3, 4, p. When the atom is excited, the electron moves to a higher orbit (black arrows). Transitions in which an electron falls to a lower level are accompanied by the emission of light. Two such transitions are shown in colors similar to those of the spectral lines they produce in the Balmer series (see Figure 7.13).
Keywords
 emission spectrum, hydrogen, electromagnetic waves, Balmer series, emission, absorbtion, line spectrum
7.20
Title
 Energy levels & spectral lines for hydrogen
Caption
 The distance between energy levels is not to scale. Three of the four visible lines in the Balmer series are shown. Each series is named for the scientist who discovered or characterized it.
Keywords
 energy levels, hydrogen, emission, spectrum, Balmer series, principle quantum number
7.21
Title
 Example 7.8 illustrated
Caption
 Several electronic transitions in a hydrogen atom are shown.
Keywords
 photon, transition, spectrum, hydrogen, atomic structure
7.22
Title
 Absorption spectrum of sunlight
Caption
 In the absorption spectrum of sunlight, some wavelengths of light appear to be missing (black bands.) Light at those wavelengths is absorbed by the gaseous components of the sun.
Keywords
 absorbtion spectrum, sun, wavelength, line spectrum
7.23
Title
 Uncertainty principle
Caption
 A free electron moves into the focus of a hypothetical microscope (a) and is struck by a photon of light; the photon transfers momentum to the electron. The reflected photon is seen in the microscope (b), but the electron has moved out of focus. The electron is not where it appears to be.
Keywords
 electron, uncertainty principle, photon, observation
7.24abcd
Title
 The 1s orbitals
Caption
 The 1s orbitals are shown in 4 different representations. (a) 1s electrons can be "found" anywhere in this solid sphere, centered on the nucleus.(b) The electron density map plots the points where electrons could be. The higher density of dots indicates the physical location in which the electron cloud is most dense.(c) Electron density (Y2) is shown as a function of distance from the nucleus (r) as a graphical representation of the same data used to generate figure b.(d) The total probability of finding an electron is plotted as a function of distance from the nucleus (r).
Keywords
 orbital, wave function, probablility, radius, 1s, electron density
7.25
Title
 An analogy to a 1s orbital
Caption
 Imagine that the hole left by each dart throw represents the probability of an electrons being at that point. If 900 of 1000 dart throws hit the board, the dartboard is analogous to the 90% outline of a 1s orbital. The greatest number of holes per unit area (say, per 1 cm2) is in the “50” regionthats what the dart thrower aims at. But what is the most likely score that the average dart thrower will make on a given throw? Can you see that the answer is “30”? Although the number of holes per square centimeter in the “30” region is smaller than in the “50” region, the total area of the “30” region is much greater. The “30” ring of the dartboard is analogous to the 52.9-pm spherical shell of the 1s orbital in the hydrogen atom.
Keywords
 electron density, probability function, atomic structure, wave function
7.26abcd
Title
 The 2s orbitals
Caption
 The 2s orbitals differ from the 1s (Figure 7.24 in the text) in having a larger volume that encompasses two regions of high electron probability separated by a spherical node, compared with a smaller, single retion of high electron probability. A 3s orbital is larger and has 2 spherical nodes.
Keywords
 atomic structure, s orbital, energy level, node, orbital, quantum mechanics
7.27
Title
 The three 2p orbitals
Caption
 The regions of high electron probabilities are dumbbell-shaped and oriented along the x, y, and z axes, respectively. Each of the orbitals has a nodal plane, a planar region of zero electron probability that passes through the nucleus of the atom.
Keywords
 p orbital, nodal plane, ml , atomic structure
7.28
Title
 The five d orbitals
Caption
 The designations xy, xz, yz, x2-y2, and z2 refer to the directional characteristics of certain combinations of the orbitals having the allowed values of ml when l=2.
Keywords
 d orbital, nodal plane, ml , atomic structure
7.29.1UN
Title
 Atoms on face of silicon crystal (STM)
Caption
 In this image made by a scanning tunneling microscope (STM), individual silicon atoms on the surface of a silicon crystal are seen at a magnification of 10 million.
Keywords
 microscopy, silica, atomic structure
7.29
Title
 Electron spin visualized
Caption
 Two possibilities for electron spin are shown with their coexisting magnetic fields. (A magnetic field is visualized in Appendix B.) The magnetic fields of two electrons with opposite spins cancel one another; there is no net magnetic field for the pair.
Keywords
 manetic field, dimagnetism, paramagnetism, electron spin, Pauli exclusion principle, atomic structure
7.30
Title
 Stern-Gerlach experiment: demonstration of electron spin
Caption
 Silver atoms vaporized in the oven are shaped into a beam by the slit, and the beam is passed through a nonuniform magnetic field. The beam splits in two. (The beam of atoms would not experience a force if the magnetic field were uniform. The field strength must be greater in certain directions than in others.)
Keywords
 magnetic field, Pauli exclusion principle, electron spin, atomic structure
7.30.2Box
Title
 Speed distribution of atoms that have formed a Bose-Einstein condensate
Caption
 Near zero Kelvin, the speed distribution of atoms drops greatly. As predicted by the Heisenburg uncertainty principle, individual atoms cannot be distinguished in postion. This phase is called the Bose-Einstein condensate.
Keywords
 absolute zero, Heisenburg, Einstein, momentum
7.P.29
Title
 Mass Spectrum
Caption
 Shown is the mass spectum from which the atomic masses of 5 naturally occuring isotopes of germanium can be determined.
Keywords
 mass spectrometer, germanium, isotope
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