Lesson 11: Quantum Model of the Atom See portions of Chapter 4 Section 2 of your textbook (pp 98-104)
Atomic Models J.J. Thompson discovery of the electron, electrons in all atoms Millikan confirmed negative charge of electron, helped determine possible mass https://www.khanacademy.org/science/physics/quantum-physics/atoms-and-electrons/a/bohrs-model-of-hydrogen
Atomic Models Rutherford most of the mass of an atom is in the nucleus, nucleus takes up very little space Niels Bohr interested in explaining the discrete line spectrum observed when light was emitted by different elements; favored planetary model https://www.khanacademy.org/science/physics/quantum-physics/atoms-and-electrons/a/bohrs-model-of-hydrogen
Remaining Questions Where are the electrons, and what are they doing? If the electrons are orbiting the nucleus, why don t they fall into the nucleus as predicted by classical physics? How is the internal structure of the atom related to the discrete emission lines produced by excited elements? https://www.khanacademy.org/science/physics/quantum-physics/atoms-and-electrons/a/bohrs-model-of-hydrogen
Demonstration: Spectral Emission Lines When an element or ion is heated by a flame or excited by electric current, the excited atoms emit light of a characteristic color The emitted light can be refracted by a prism, producing spectra with a distinctive striped appearance due to the emission of certain wavelengths of light https://www.khanacademy.org/science/physics/quantum-physics/atoms-and-electrons/a/bohrs-model-of-hydrogen
Bohr Model of the Atom Proposed in 1915 by Niels Bohr. 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. https://www.khanacademy.org/science/physics/quantum-physics/atoms-and-electrons/a/bohrs-model-of-hydrogen
Bohr Model of the Atom In the Bohr model of the atom, electrons travel in defined circular orbits around the nucleus.
Some problems with the Bohr Model Does not work for systems with more than one electron. It violates the Heisenberg Uncertainty Principle because it considers electrons to have both a known radius and orbit. The Bohr Model provides does not predict the of relative intensities spectral lines.
Electrons have wave-like properties Light can behave as. both a wave and a particle Electrons have dual properties as well! DeBroglie: Electrons considered as waves confined to the space around an atomic nucleus bent Electrons can be, or diffracted
The speed and position of an electron cannot be measured simultaneously. Electrons are detected by. their interaction with photons (light!) Photos and electrons have about the same. energy Therefore, photons. knock electrons of their course It is impossible to determine simultaneously both the position and velocity of an electron
Heisenberg Uncertainty Principle It is impossible to determine simultaneously both the position and velocity of an electron
Orbitals indicate probable electron locations Schrödinger used the hypothesis that electrons have a dual wave-particle nature to develop an equation that treats electrons as waves
Orbitals indicate probable electron locations Orbital = three dimensional region around the nucleus that indicates the probable location of an electron See figure 2.2 in textbook (p.101)
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Energy Level = n main energy level The occupied by the electron Are positive integers (1, 2, 3, etc.) As n increases, the electron s energy and average distance from the nucleus increases Which electron is closest the nucleus? e- A with n =1 OR e- B with n =2 More than one electron can have the same n value.
Nucleus
Nucleus n=1 n=2 n=3 n=4
Orbital Shape = s, p, d This is the most probable locations for electrons s orbital p orbital d orbital See figure 2.5 in textbook
Nucleus s n=1
p Nucleus s s n=1 n=2
2p Nucleus 1s 2s
3d Nucleus 2p 3p 1s 2s 3s
Electron Spin Electrons exist in one of two possible spin states: + 1 2 or - 1 2 two electrons A single orbital can hold a maximum of. opposite spin states The two electrons must have.
1, 2, 3, 4 = energy levels, electron shells s,p,d,f = sublevels each box = orbital each = electron 3d Nucleus 2p 3p 1s 2s 3s
The Bus Rule
Video on Electrons: https://www.youtube.com/watch?v=rckile9cdaa&index=5&list=pl8dpuualjxtphzzyuwy6fyeax9mqq8ogr
Do Now: Take your CJs out copy down info from CJ board Keep CJs out and open COPY & answer the following questions in Box 1 of your notes packet: 1. Calculate: 2.0 cm x 1.00 cm x 8 cm = 2. Define atomic mass. 3. One mol of NaCl = atoms 4. What is the molar mass of Argon (Ar)? 5. What is the mass of 6.022 x 10 23 iron (Fe) atoms?
Do Now: Take your CJs out copy down info from CJ board Keep CJs out and open COPY & answer the following questions in Box 2: What are spectral emission lines? Describe the Bohr model. What is a photon?
Do Now: Take your CJs out copy down info from CJ board Keep CJs out and open COPY & answer the following questions in Box 2 of your Lesson 11 notes packet: 1. How do you determine the number of electrons?. in a neutral atom? in an ion? in an isotope? 2. One mole of helium atoms = moles of electrons