KU CHEM 130 - Chapter 7: The Quantum-Mechanical Model of the Atom

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Chapter 7: The Quantum-Mechanical Model of the Atom7.2 The Nature of Light- Light have many common characteristics with electrons.- Wave-particle duality is certain properties can be described using waves while other properties are better described with particle.The Wave Nature of Light- Light is electromagnetic radiation, a type of energy embodied in oscillating electric and magnetic field.- Magnetic field is where a magnetic particle experience force while electric field is a region where electrically charged particle experience force.- Proton has an electric field.- Light travels 3.00*108 m/s while sound travels 340 m/s.- Amplitude of wave is height of crest or depth of trough.- Wavelength is the distance between two crests or two troughs.- Greater amplitude and shorter wavelength has more energy.- Amplitude determine brightness and wavelength determine color.- Amplitude and wavelength are independent properties.- Frequency is measured by number of cycles per second (s-1).- 1 Hz = 1 s-1- Frequency is inversely proportional to wavelength. Longer the wavelength, the less the frequency.- Frequency (v) = (speed of light m/s) / (wavelength m)- Red light has longest wavelength and violet has the shortest wave length.The Electromagnetic Spectrum- Electromagnetic spectrum includes all wavelength of electromagnetic radiation.- Short wavelength has greater energy than long wavelength.Interference and Diffraction- Interference is when waves build each other up or cancel each other out depending on alignment.- Constructive interference is when two waves of equal amplitude align with overlapping crests to result in a wave with twice the amplitude.- Destructive interference is when two waves align in such a way that the trough of one wave overlaps with the crest of another wave to result in the waves canceling out.- Diffraction is when a wave encounters an obstacle or slit and bends around it.- Interference pattern is light diffracted through two slits separated by a distance to produce two new waves that interfere with each other.- Pattern of dark and light lines are recorded on a film.- Dark lines are destructive interference and light lines are constructive interference.Particle Nature of Light- Photoelectric effect is metals emit electrons when light shines upon them.- Classical electromagnetic theory (classical mechanics) attributed the photoelectric effect to the transfer of energy from light to electron in metal to dislodge it.- Found to be inadequate and didn’t explain photoelectric effect or Black Body Radiation.- Photoelectric effect, electrons only emitted by light with frequency above certain threshold and energy of electron increase with frequency and not intensity of light.- Albert Einstein proposed that light energy come in packets called photon or quantum that behaves as particles with energy.- Energy of a Photon (J) = (Planck’s constant J*s) (frequency s-1)- Electron is bound to a metal with energy x and if the threshold frequency is reached, the energy of photon equals x.- One photon has enough energy to dislodge electron.- Kinetic energy of ejected electron is energy of photon minus the binding energy.7.3 Atomic Spectroscopy and the Bohr Model- Atomic spectroscopy is electromagnetic radiation absorbed and emitted by atoms.- When an atom absorbs energy, it re-emits that energy.- Emission spectrum is the light emitted by an element which can identify the element.- Different elements have different wavelengths to produce different emission spectrums.- White light has a continuous spectrum with all wavelengths.- Emission spectrum consist of discrete lines because stationary states exist only at specific energies.- Photon is absorbed when electron goes to a higher energy level and photon is emitted when electron drops to a lower energy level.- Lyman series is when an electron drops to n=1 energy level.- Produce ultraviolet rays.- Balmer series is when an electron drops to n=2 energy level.- Produce visible light.- Paschen series is when an electron drops to n=3 energy level.- Produce infrared rays.- LASER = Light Amplification by the Stimulated Emission of Radiation.- [A+] greater than [A]. (Inverted population)- Optical cavity where majority of emitted photons are reflected back to stimulate more emission.7.4 The Wave Nature of Matter: De Broglie Wavelength, Uncertainty Principle, Indeterminacy- Louis de Broglie proposed the wave nature of electrons.- The wave nature of electron is an inherent property of a single electron.The de Broglie Wavelength- Wavelength (m) = (Planck’s Constant J*s) / (mass kg) (velocity m/s)- Mass of electron is 9.11*10-11-2πr = nλUncertainty Principle- Wave and particle nature of electron are complementary properties meaning the more we know one, the less we know about the other.-Δx × mΔv ≥h4π-Δx is uncertainty in position, Δis uncertainty in velocity, m is mass (kg), and h is Planck’s constant.- Electron is observed either as a particle or a wave but never both at once.Indeterminacy- Probability distribution map is a map that show where an electron is most likely to be found.- The exact position of an electron cannot be determined.7.5 Quantum Mechanics and the Atom- Position and energy are also complementary properties.- Energy specified precisely and electron position described in orbitals, a probability distribution map.Solutions to the Schrodinger Equation- Each electron orbital is specified by three interrelated quantum numbers: principal quantum number (n), angular momentum quantum number (l), and magnetic quantum number (ml). A fourth quantum number, the spin quantum number (ms) specify orientation of electron spin.- If orbitals have the same value of n, the are in the same principal level.- If orbitals have the same value for n and l they are in the same sublevel.- Number of sublevel is equal to n.- Number of orbitals in sublevel is 2l + 1- Number of orbitals in level is n2.Principle Quantum Number (n)- It is the integer that that determine the overall size and energy of an orbital.- n = 1, 2, 3, etc...Angular Momentum Quantum Number (l)- It determines the shape of the orbital.- l = 0, 1, 2, 3 .... (n-1)- For a value of n, l can be any integer up to n-1, including 0.- l = 0 is s, 1 = 1 is p, l = 2 is d, l = 3 is f.Magnetic Quantum Number (ml)- It is an integer that specify orientation of orbital.- Ranges from -l to +l.Spin Quantum Number (ms)- It specify orientation of the spin of the electron.- It has two possibilities:


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KU CHEM 130 - Chapter 7: The Quantum-Mechanical Model of the Atom

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