General Chemistry Ch. 7 - Quantum Theory and Atomic Structure
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| show | Energy propagated by means of electric and magnetic fields that alternately increase and decrease in intensity as they move through space.
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| show | Frequency and wavelength
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| show | Symbol nu, is the number of cycles the wave undergoes per second and is expressed in units of 1/second, or S^-1, AKA hertz (Hz).
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| Wavelength | show 🗑
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| show | ALL types of electromagnetic radiation travel at the same speed: 299,792,458 m/s, the speed of light (c).
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| show | c = nu * lambda. I.e. frequency * wavelength.
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| Amplitude of a wave | show 🗑
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| The dimness/brightness of light is related to its | show 🗑
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| Electromagnetic spectrum | show 🗑
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| show | Radio waves, microwaves, infrared, visible(red -> violet), ultraviolet, x-ray, gamma rays.
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| How should you quantitatively refer to wavelength regions? | show 🗑
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| What phenomenon describes why electromagnetic radiation travels at different velocities through different media (e.g. vacuum vs. air vs. water) | show 🗑
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| show | A phenomenon in which a wave changes its speed and therefore its direction as it passes through a phase boundary.
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| Why does light split into different colors as it passes through a prism (this is called dispersion of light)? | show 🗑
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| show | Light refracted through the droplets hit your eye at different angles depending on the distance the droplet it from your eye. The droplets closest to you (closest to the ground) are being refracted at the most acute angles.
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| How does refraction of energy differ from the behavior of particles | show 🗑
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| Diffraction | show 🗑
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| show | When energy passes through a slit, it bends around both edges of the slit and forms a semicircular wave on the other side of the opening.
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| show | If waves of light pass through two adjacent slits the emerging circular waves interact with each other through the process of interference.
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| Interference pattern results from… | show 🗑
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| How does the interference pattern differ from particle movement | show 🗑
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| Three phenomena involving matter and light that confounded physicists at the turn of the 20th century | show 🗑
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| show | A blackbody is an idealized object that absorbs all the radiation incident on it.
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| show | Light given off by a hot blackbody
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| What did Max Planck propose about hot blackbodies? | show 🗑
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| If an atom itself can have only certain quantities of energy, then… | show 🗑
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| show | Plural: quanta, are “packets”, or definite amounts of, energy.
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| show | Emitting (or absorbing) one or more quanta.
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| show | The difference in the atom’s energy states: deltaE_atom = delta(n*h*nu)
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| Equation describing when an atom in a given energy state changes to a single adjacent state | show 🗑
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| The photoelectric effect | show 🗑
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| show | (1) The presence of a threshold frequency and (2) the absence of a time lag
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| Photoelectric effect: The presence of a threshold frequency | show 🗑
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| show | Current flows from the moment light of this minimum frequency shines on the metal, regardless of the light’s intensity. The wave theory predicts there would be a time lag before the current so the electron could break free
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| show | Einstein proposed that light itself is particulate, that is, quantized into small bundles of electromagnetic energy, later called photons.
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| Energy of a photon | show 🗑
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| show | A beam of light consists of a large number of photons. Brightness is related to the number of photons striking a surface per unit time. A photon of certain minimum energy must be absorbed for an electron to be freed.
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| show | An electron cannot “save up” energy from several photons below the minimum energy until it has enough to break free, rather one electron breaks free the moment it absorbs one photon of enough energy (hence: quantized).
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| Current is weaker in dim light than bright light because… | show 🗑
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| show | Fixed quantity and discrete particles
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| show | The photon model doesn’t replace the wave model; we must accept both as reality.
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| Line spectrum | show 🗑
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| show | 1. The H atom has only certain allowable energy levels, 2. The atom does not radiate energy while in one of its stationary states, and 3. The atom changes to another stationary state only be absorbing or emitting a photon…
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| show | Energy levels whereby each of these states is associated with a fixed circular orbit of the electron around the nucleus.
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| How does an atom change to another stationary state? | show 🗑
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| Lower energy level of an atom means that its electron… | show 🗑
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| show | Ground state
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| When an electron is in the second or any higher orbit, the atom is said to be in an… | show 🗑
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| show | (1) The illustrated model of the H atom is incorrect, (2) the math only predicts the bands for one-electron species because electron repulsions and attractions are present in those with more than one electron.
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| Equation for calculating the energy levels of an atom | show 🗑
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| show | h*nu = -2.18^-18*(1/n^2_final – 1/n^2_initial), and since h*nu = hc/lambda, thus: 1/lambda = ((-2.18^-18)/hc)*(1/n^2_final – 1/n^2_initial)
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| Calculating Ionization energy of an atom | show 🗑
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| show | The quantity of energy required to form 1 mol of gaseous H+ ions from 1 mol of gaseous H atoms
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| Louis de Broglie’s proposal about matter in the early 1920s | show 🗑
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| show | Louis de Broglie combined Einstein’s mass equivalence (E=mc^2) with Planck’s photon energy (E=hc/lambda) to obtain lambda = (h/mu) where h = constant, m = mass and u = speed.
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| show | That matter travels in waves, and that the wavelength is inversely proportional to the object’s mass and speed.
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| So if electrons travel in waves, then they should display… | show 🗑
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| show | We can calculate momentum (p), the product of mass and speed, for a photon of a given wavelength. Substitute c for you and re-write de Broglie’s equation: lambda = h/p, solve for p: p = h/lambda
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| show | The inverse relationship between p and lambda means that shorter wavelengths should have greater momentum. Thus, a decrease in a photon’s momentum should appear as an increase in its wavelength.
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| show | In 1923, Arthur Compton directed a beam of x-ray photons at a sample of graphite and observed that the wavelength of the reflected photons increased. This means the photons transferred some of their momentum.
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| show | That both matter and energy show both behaviors; each possesses both “faces”.
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| The dual character of matter and energy is known as | show 🗑
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| Uncertainty principle | show 🗑
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| show | Then the less accurately we know its speed (larger deltaU). Thus, unlike classical physics, we can’t calculate the exact trajectory of an electron.
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| show | It means that we cannot assign fixed paths for electrons, such as the circular orbits of Bohr’s model. All we can ever hope to know is the probability of finding an electron in a given region of space.
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| show | The branch of physics that examines the wave motion of objects on the atomic scale
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| show | He derived a model that describes an atom that has certain allowed quantities of energy due to the allowed frequencies of an electron whose behavior is wavelike and whose exact location is impossible to know.
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| Schrodinger equation | show 🗑
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| In the Schrodinger equation what does psi and the Hamiltonian operator represent? | show 🗑
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| show | …the given atomic orbital.
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| show | “orbital” in the quantum-mechanical model bears no resemblance to an “orbit” in the Bohr model: an orbit was an electron’s path around the nucleus, whereas, an orbital is a mathematical function with no direct physical meaning.
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| The Schrodinger equation allows us to… | show 🗑
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| Psi^2 | show 🗑
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| Electron density diagram | show 🗑
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| Summary of the result of an electron density diagram | show 🗑
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| show | A chart that shows the layers around an atom and the dots where the electrons might be found according to their probabilities
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| Probability contour | show 🗑
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| show | A distinctive radial probability distribution and 90% probability contour.
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| An atomic orbital is specified by… | show 🗑
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| Principal quantum number (n) | show 🗑
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| Angular momentum quantum number (l) | show 🗑
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| show | An integer from -l (the letter) through 0 to +l. It describes the orientation of the orbital in the space around the nucleus and is sometimes called the orbital-orientation quantum number. Thus if l is 2, m_l = -2 through +2
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| If n = 3, how many orbitals are there | show 🗑
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| show | The n value: the smaller the n value, the lower the energy level and the greater the probability of the electron being closer to the nucleus.
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| Energy sublevels (or subshells) | show 🗑
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| Sublevels are named by… | show 🗑
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| Orbital | show 🗑
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| show | 1s orbital: spherical, highest probability density at nucleus, 2s orbital larger sphere, highest probability farther away from nucleus, 3s orbital: even larger sphere, highest probability density farther from nucleus.
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| s orbital node | show 🗑
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| show | Has two regions (lobes) of high probability, one on either side of the nucleus. The nucleus lies at the nodal plane of the dumbbell-shaped orbital. Only levels with n = 2 or higher can have a p orbital. An electron spends equal time in each lobe.
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| show | 2p.
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| show | Unlike an s orbital, each p orbital does have a specific orientation in space. Each m_l value refers to three mutually perpendicular p orbitals. They correspond with the x, y, and z axes: p_x, p_y, and p_z
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| d orbital: shape and description | show 🗑
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| show | l = 3 are f orbitals and must have a principal quantum number of at least n = 4. There are seven f orbitals, each with a complex multilobed shape. l = 4 are g orbitals. we will not discuss those because they play no role in bonding
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| show | The energy state of the H atom depends only on the principal quantum number, n. For the H atom only, all four n = 2 orbitals have the same energy, all nine n = 3 orbitals have the same energy, etc.
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