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The Electron

The Electron. Part 2. The Quantum Model of the Atom. In 1927, Werner Heisenberg proposed his uncertainty principle. You can’t know both the velocity & position of a particle at the same time

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The Electron

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  1. The Electron Part 2

  2. The Quantum Model of the Atom • In 1927, Werner Heisenberg proposed his uncertainty principle. • You can’t know both the velocity & position of a particle at the same time • Meaning we can’t predict the exact location of an e- or it’s path in the atom • Whatever you use to measure the location of an electron will cause the electron to move

  3. To detect the position of an electron you might use a photon. Unfortunately, when the photon collides with the electron the force of the collision causes the electron to change position, so the best you can tell is where the electron was.

  4. The Quantum Model of the Atom • The biggest effect of the Uncertainty Principle on Bohr’s model is that there is no way to define the path of the e- around its nucleus with any accuracy. • The best we can do is make an educ-ated guess within a certain range of probability that the e- is in a particular region around the nucleus.

  5. The Quantum Model of the Atom • In 1926, the physicist Erwin Schrod-inger took the atom 1 step further. • He proposed a mathematical equation to describe the location & energy of the e- in a H atom. • He used calculated the “wave func-tion” of the e-, or the probability of locating the e- a certain distance from the nucleus • the quantum mechanical model is based on Schrodinger’s work.

  6. The Quantum Model of the Atom

  7. The Quantum Model of the Atom • Like the Bohr model, the quantum mech model of the atom restricts the energy of e-’s to quantized values. • But, the quantum mechanical model doesn’t define a specific path an elec-tron takes around the nucleus. • Instead it estimates the probability of finding an electron in a certain position.

  8. Bohr’s model gave the e- specific paths around the nucleus, based on the energy of the electron However, we can only guess within a certain degree of probability the location of an e-

  9. The Quantum Model of the Atom • The probability of finding an electron within a certain volume of space surrounding the nucleus can be represented by a fuzzy cloud • The cloud is more dense where the probability of finding the e-is higher.

  10. The Quantum Model of the Atom • Each electron in a given atom is given a set of 4 values called quantum numbers, that describe an electron’s behavior. • The 1st 3quantum numbersmap the electron’s location, the 4th describes the electron’s orientation. • No 2 electronshave an identical set of four quantum numbers.

  11. The Quantum Model of the Atom • You can assign every electron in a given atom (element) a set of 4 quan-tum numbers • The quantum numbers act as the electron’s address in the atom. • Quantum #’s can be described as a kind of coordinate system to map the location of an e- in the atom.

  12. The Quantum Model of the Atom • The problem with e- in the atom is that they can’t be pinned down to a precise location because of Heisen-berg’s Uncertainty Principle • So the quantum #’s only give a fuzzy or probable location of the electron in the atom.

  13. The Electron is here The Quantum Model of the Atom • An analogy of quantum numbers might help. • We can think about the quantum #’s as perhaps like trying to find our seat in Rupp Arena using a ticket stub.

  14. The Quantum Model of the Atom • Each piece of information on your ticket stub gets you closer and closer to your seat. • Each quantum number gets us closer and closer to the probable location of an electron

  15. The Quantum Model of the Atom • The 1st quantum number is the “Principle Quantum Number” • symbolized by n. • can values of 1 to infinity. • The larger the value of n, the farther from the nucleus the electron is. • These electrons are moreenergeticso the volume of their appearance is larger

  16. The Quantum Model of the Atom • Each energy level has a limit to the number of electrons it can hold. • n=1 can hold2 electrons • n=2 can hold8 electrons • n=3 can hold8 electrons • n=4 can hold18 electrons • n=5 can hold18 electrons • n=6 can hold32 electrons

  17. The Quantum Model of the Atom • The Principle quantum number can be compared to the level of Rupp. • The Upper Arena is farther from the floor than the Lower Arena • The larger the principal quantum number the farther from the nucleus.

  18. The Quantum Model of the Atom • The 2nd Quantum number is the “Azimuthal Quantum number” • Symbolized with an “l,” • can have numbers of 0, 1, 2, 3 which correspond to the letters s, p, d, f. • indicates a shape of an orbital • “l” is expressed withlettersrather than numbers. • An s orbital is spherical • A p orbital is dumb-bell • A d is mostly clover-leaf • An f is really complicated

  19. The Quantum Model of the Atom • Each l is called an orbital • An orbital is the region or volume around the nucleus of an atom where an electron with a given energy is likely to be found.

  20. The Quantum Model of the Atom • Every energy level (quantum # - n) contains 1 and only 1 s sublevel • The number of sublevels in any given n is theoretically related to the value of n • n=1has 1 sublevel…only the s • n=2 has 2 sublevels…s & p • n=3 has 3 sublevels…s, p, & d • n=4 has 4 sublevels…s, p, d, & f

  21. The Quantum Model of the Atom • The quantum # l might correspond to the section number on our stub • It narrows down for us to the specific area in the upper arena that our seat is in. • The l quantum number gives us the sublevel of the electron on the energy level.

  22. The Quantum Model of the Atom • The 3rd Quantum number is the “Orientation/Orbital quantum number” • Symbolized by ml • Within each sublevel, are orbitals – each with a different orientation. • Each orbital higher than ml= 1 can have a different orientation on the Cartesian axis (x, y, & z)

  23. The Quantum Model of the Atom • On a map ml might be thought of as the row our seat is located on. • The row narrows down for us where in the section our seat is. • In the atom, mlgives the direction that the shape of the volume that the electron occupies points.

  24. The Quantum Model of the Atom • Together the l and ml quantum numbers give valuable info about the electrons probable location • The “s” sublevel (l =0; ml = 0): • Spherical shape and only oneallowed in each energy level. • As the energy increases (n) the “s” orbital also getsbigger.

  25. The Quantum Model of the Atom • The p-sublevel: (l =1; ml=-1,0, or 1) • Shaped like adumbbell. • There are 3 orbitals designated px, py, or pz in each energy level. (Based on axis on the cartesian coordinates) • The p orbitals are higherenergythen s orbitals • Only found in ground state atoms containing 5 electrons or more

  26. The Quantum Model of the Atom • The d-orbital (l =2; ml= -2, -1, 0, 1, 2): • The d orbitals have more complicated shapes. • There are5-dorbitals in each energy level that they appear. • The d-orbitals appear only after the 2nd energy level, and beyond

  27. Proposed composite of 5 d-orbitals

  28. The Quantum Model of the Atom • The f-orbital (l = 3; ml = -3, -2, -1, 0, 1, 2, 3) • Most energetic and complicated • There can be7 “f”orbitals for each energy level that they occupy.

  29. The Quantum Model of the Atom • There is a limit to how many electrons that each sublevel can hold, which limits the number of electrons that can have the same relative energy

  30. The Quantum Model of the Atom • The 4th and final Quantum Number, is the Spin quantum number • Symbolized by ms • Each orbital can hold at most 2 electrons, • They must spin in opposite directions on their axes designated (+½ & -½)

  31. The Quantum Model of the Atom • The spin quantum number might work somewhat like the seat number on the ticket stub. • There is only one possible seat that corresponds to the information on your ticket. • There is only one possible electron that matches a given set of quantum numbers

  32. The Quantum Model of the Atom Set of (n, l, ml, ms) • H only has 1 electron, and it is on the n=1 energy level, and it’s in the s-sublevel • (1,0,0,+½) • He has 2 electrons, and they are both on the n=1 energy level, and in the s sublevel • (1,0,0,+½)(1,0,0,-½)

  33. The Quantum Model of the Atom • Lithium has an electron in the n=2 energy level and so on…. • 3Li: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) • 4Be: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) • 5B: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½)

  34. The Quantum Model of the Atom • Continuing With n=2 • 6C: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½) (2,1,0,+½) • 7N: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½) (2,1,0,+½) (2,1,1,+½)

  35. The Quantum Model of the Atom • 8O: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½) (2,1,0,+½) (2,1,1,+½) (2,1,-1,-½) • 9F: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½) (2,1,0,+½) (2,1,1,+½) (2,1,-1,-½) (2,1, 0,-½)

  36. The Quantum Model of the Atom • 10Ne: (1,0,0,+½) (1,0,0,-½) (2,0,0,+½) (2,0,0,-½) (2,1,-1,+½) (2,1,0,+½) (2,1,1,+½) (2,1,-1,-½) (2,1, 0,-½) (2,1,1,-½)

  37. Not every orbital is found in every energy level. (ie.The n=1 level only contains the s orbital)

  38. Electron Configurations • The distribution of electrons among the energy levels, sublevels, orientations, and spins of an atom is known as the electron configuration. • Having a basic understanding of how the electrons are configured helps us determine the interaction of atoms of elements to other elements • When they come into contact it’s theouter electronsthat do the chemistry.

  39. Electron Configurations • Electron configurations are determin-ed by distributing electrons among levels, sublevels, & orbitals, in order of lowest in energy to highest. • We can predict the location of the electrons in the atoms by following 3 important principles:

  40. Electron Configurations • The Aufbau Principle • Electrons are added one at a time to thelowest energyorbitals available until allelectronsare distributed. • The # of electrons distributed, depends on the atomic # of the atom. • We’ll use a diagram to help placement in the proper order

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