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November 13, 2007

November 13, 2007. Please staple both labs together and place in basket. Spectra lab 1 st , Flame test 2 nd Then review by completing the following: Name the 4 orbitals Draw the 4 orbital shapes Define an orbital

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November 13, 2007

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  1. November 13, 2007 Please staple both labs together and place in basket. Spectra lab 1st, Flame test 2nd Then review by completing the following: Name the 4 orbitals Draw the 4 orbital shapes Define an orbital Today in class, we will continue to describe electrons using the quantum mechanical model of the atom. Homework:Important Dates: LEQ 11/29- Ch5 Test Read Ch5 11/26- E.C. due (pg 130) Study Guide

  2. Quantum Mechanical Model From Bohr to present

  3. 6.5 Quantum Mechanical Atom • Electrons are outside the nucleus • Electrons can’t be just anywhere – occupy regions of space • Knowing the location and energy of an electron ( a wave) is limited in accuracy • Heisenberg Uncertainty Principle • Orbitals • Regions in space where the electron is likely to be found • Regions are described mathematically as waves

  4. Schrodinger Wave Equation • In 1926 Schrodinger wrote an equation that described both the particle and wave nature of the e- • Wave function (Y) describes: • . energy of e- with a given Y • . probability of finding e- in a volume of space • Schrodinger’s equation can only be solved exactly for the hydrogen atom. Must approximate its solution for multi-electron systems. Solutions to wave functions require integer quantum numbers n, l and ml. 7.5

  5. Y = fn(n, l, ml, ms) • Solutions to wave functions require integer quantum numbers n, l and ml • Quantum numbers are much like an address, a place where the electrons are likely to be found Each distinct set of 3 quantum numbers corresponds to an orbital

  6. QUANTUM NUMBERS The shape, size, and energy of each orbital is a function of 3 quantum numbers which describe the location of an electron within an atom or ion n (principal) ---> energy level l(angular momentum) ---> shape of orbital ml(magnetic) ---> designates a particular suborbital The fourth quantum number is not derived from the wave function s(spin) ---> spin of the electron (clockwise or counterclockwise: ½ or – ½)

  7. n=1 n=2 n=3 Schrodinger Wave Equation Y = fn(n, l, ml, ms) principal quantum number n n = 1, 2, 3, 4, …. distance of e- from the nucleus 7.6

  8. Where 90% of the e- density is found for the 1s orbital e- density (1s orbital) falls off rapidly as distance from nucleus increases 7.6

  9. Schrodinger Wave Equation Y = fn(n, l, ml, ms) angular momentum quantum number l for a given value of n, l= 0, 1, 2, 3, … n-1 l = 0 s orbital l = 1 p orbital l = 2 d orbital l = 3 f orbital n = 1, l = 0 n = 2, l = 0 or 1 n = 3, l = 0, 1, or 2 Shape of the “volume” of space that the e- occupies 7.6

  10. Types of Orbitals (l) s orbital p orbital d orbital l = 0 l = 1 l = 2

  11. l = 0 (s orbitals) l = 1 (p orbitals) 7.6

  12. p Orbitals this is a p sublevel with 3 orbitals These are called x, y, and z There is a PLANAR NODE thru the nucleus, which is an area of zero probability of finding an electron 3py orbital

  13. p Orbitals • The three p orbitals lie 90o apart in space

  14. l = 2 (d sublevel with 5 orbitals) dOrbitals 7.6

  15. f Orbitals For l = 3 f sublevel with 7 orbitals

  16. Schrodinger Wave Equation Y = fn(n, l, ml, ms) magnetic quantum number ml for a given value of l ml = -l, …., 0, …. +l if l = 1 (p orbital), ml = -1, 0, or1 if l = 2 (d orbital), ml = -2, -1, 0, 1, or2 orientation of the orbital in space 7.6

  17. ml = -1 ml = 0 ml = 1 ml = -2 ml = -1 ml = 0 ml = 1 ml = 2 7.6

  18. Schrodinger Wave Equation Y = fn(n, l, ml, ms) spin quantum number ms ms = +½or -½ ms = +½ ms = -½ 7.6

  19. Schrodinger Wave Equation Y = fn(n, l, ml, ms) Existence (and energy) of an electron in an atom is described by its unique wave function Y. Pauli exclusion principle- no two electrons in an atom can have the same four quantum numbers. • Each seat is uniquely identified (E1, R12, S8) • Each seat can hold only one individual at a time 7.6

  20. How many electrons can an orbital hold? Schrodinger Wave Equation Y = fn(n, l, ml, ms) Shell – electrons with the same value of n Subshell – electrons with the same values of nandl Orbital – electrons with the same values of n, l, andml If n, l, and mlare fixed, then ms = ½ or - ½ Y = (n, l, ml, ½) or Y = (n, l, ml, -½) An orbital can hold 2 electrons 7.6

  21. Summary • An electron has a 100% probability of being somewhere • ORBITAL: The region in space where an electron is likely to be found • The usual pictures of orbitals show the regions where the electron will be found 90% of the time http://www.falstad.com/qmatom/

  22. Summary 7.6

  23. How many 2p orbitals are there in an atom? n=2 n=3 l = 1 l = 2 How many electrons can be placed in the 3d subshell? If l = 1, then ml = -1, 0, or +1 2p 3 orbitals If l = 2, then ml = -2, -1, 0, +1, or +2 3d 5 orbitals which can hold a total of 10 e- 7.6

  24. Summary Compare and contrast the Bohr and quantum mechanical models.

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