Chemistry Videos Chapter 7 Quantum Theory and Atomic Structure Rutherford Nucleus and electron attract each other remain apart electron must move KE of Electron s motion must balance PE of attraction The Nature of Light Electromagnetic waves originate from the movement of electrical charges Causes fluctuations in electrical fields Electromagnetic waves require no medium Frequency V nu of cycles a wave makes per second units of S 1 or Hertz Wavelength lamda upside down Y dist btwn any point on a wave and corresponding point on next wave C lamda meters x nu s 1 Freq and wavelengths are inversely related C speed of propogation C speed of light in a vacuum Memorize regions of the electromagnetic spectrum Gxu Vimr Visible is 400 violet 750 red Skill Interconverting frequency and wavelength convert to meters C will always be 3 00 x 10 8 m s V c lamda Plug in Blackbody Heat Radiation Object heated red then orange then white light Max Planck 1900 proposed that hot solids can emit energy only in discrete quantities E energy produced in J n discrete x h Planck s Constant 6 626 x 10 34 x v frequency Delta E DeltaN x h x v if deltaN 1 DeltaE h x v radiation Energy of atoms not continuous but quantized only exist at discrete energies Each change results in a packet of energy being gained or lost by the atom This energy packet a quantum DeltaE atom E quantum DeltaE atom E radiation h x frequency radiation these are magnitudes not considered positive or negative The photoelectric effect Einstein Used Planck s quantum idea Packets called photons E photon h Planck s constant x frequency photon Skill Interconverting energy of a photon with its frequency and or wavelength E photon H planck s constant x V frequency Planck s x C speed of light wavelength Atomic Spectra Excited atoms emit light frequency values characteristic of the atom Different atoms produce different types of photons have info on atom s energy levels Hydrogen atom produces great series of lines Rydberg equation gave the wavelengths of lines 1 wavelength Rydberg constant 1 n1 2 1 n2 2 Rydberg Constant 1 096776 x 10 7 m 1 N1 and n2 are positive integers n2 n1 Skill Using Rydberg s Equation Plug in and solve Remember to convert Nanometers 10 9 1 meter Niels Bohr Created model for the hydrogen atom that predicted line spectrum of hydrogen Each state was associated with circular orbit of the electron around the nucleus Bohr proposed H atoms do not radiate energy while in one of fixed energy states When the electron moves to a different orbit the atom changes to another energy state n initial n final As this happens the atom absorbs or emits a photon The magnitude of photon energy equals the difference in energy between the two stationary states E photon Efinal E initial Planck s constant x frequency photon hc wavelength photon Spectral lines due to emission of photons of specific energies as electron drops from higher to lower state rewatch till 30 00 Skill calculating wavelength with Rydberg s DeltaE atom E final state E initial state Delta E atom E n1 E n2 E photon deltaEatom deltaEatom Energy states of the hydrogen atom E 2 18 x 10 18 1 n 2 E 0 occurs when n infinity electron fully removed from the nucleus So E 0 for all n values infinity Transition energy E final E initial Delta E atom 2 18 x 10 18 1 nfinal 2 1 ninitial 2 Looks like Rydberg Bohr model worked for one electron species but NOT for ions with more than one electron Wave Particle Duality of Matter and Energy Louis de Broglie Plucked guitar string Fixed energy states Subatomic particles such as electrons may exhibit properties of waves If electrons are wavelike held in orbits of fixed radii only certain wavelengths energies would be allowed Wavelength h mu Where m is mass and U is velocity Object s wavelength is inversely related to mass heavy objects have lambda much smaller than the object Fast moving electrons have calculated wavelengths close to size of an atom How particles and waves differ the phenomena of diffraction and interference Wave Diffraction If a wave passes through a slit about as wide as it s wavelength it forms a semicircular wave If flight waves pass through two adjacent slits the emerging circular waves interact through interference creating a diffraction pattern Electrons DO behave as waves because they exhibit these wave properties Heisenberg wave and particle properties how determine position Uncertainty principle can t determine exact position and exact energy of wave particle simultaneously Picked energy Electron density So QM cannot describe exact paths for electrons at best probability of finding an electron in a given volume of space can be determined The Quantum Mechanical Model of the Atom Schrodinger developed quantum mechanical model of the H atom 3D wave math Wave behavior of electron leads to an H atom with the same fixed energy states See energy diagram in Fig 7 21 Structure shells subshells orbitals Solutions of Schrodinger s wave equation are math fxns that describe atomic orbitals Each describes a fixed E state electrons can occupy Schrodinger s Quantum Numbers n l mi Principal quantum number n is a positive integer not to 0 N value specifies the energy level shell in the H atom and the size of the orbitals Angular momentum quantum number l is an integer between 0 and n 1 L dictates type of subshell and shape of its orbitals In shells with n 2 l takes value of 0 or 1 two subshells The number of different l values equals the value of n DON T FORGET THAT 0 COUNTS AS A Magnetic quantum number m is an integer taking values from l through 0 to 1 M prescribes the orientation of the orbital in the 3D space about the nucleus When l 0 m 0 only L 1 m has values of 1 0 1 Tip the of possible m values orbitals for a given l value is 2l 1 Skill Determining quantum s for an energy level Total of orbitals in a given shell is n 2 L 0 is S subshell these are spherical L 1 is P subshell two regions of high electron density dumbbell 2P orbitals are equal in size shape and energy Differ only in orientation Nucleus lies on a nodal plane L 2 is d subshell Clover looking Recognize from each angle Dzx Dzy ETC L 3 is f subshell The subshell with n 2 and l 0 is called 2s Skill determining quantum numbers and sublevel designations Energy levels of the hydrogen atom Schrodinger In the ground state N 1 Higher levels converge in E E 2 18x10 18 1 n 2 The excited atom can return to the ground state emitting a photon fuck gotta know some history