Post on 06-Apr-2018
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CHEM105-05
Chapter 8 (8.1 8.3)
2 - November - 2008
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Quantum numbers andatomic orbitals
Principle quantum number (n):
- referred to as principle shell
- only positive integers allowed
- higher numbers = higher energy level
Orbital angular momentum quantum number (l)
- referred to as subshell
- l= 0,1,2,(n-1) 0,1,2,3 = s,p,d,f
Magnetic quantum number (ml):
- determines orientation in space of orbitals in given type of subshell- can have any integral value from -lto +l
Electron spin quantum number (ms):
- describes motion of electron with respect to magnetic field it induces
- can have value of either +1/2 () or -1/2 ()
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Review of orbital sub-shells
sorbitals
spherical
1 per shell
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Review of orbital sub-shells
porbitals
barbell
3 per shell
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Review of orbital sub-shells
dorbitals
multiple
shapes
5 per shell
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orbital energy diagrams
in hydrogen atoms, all subshells of a principalshell are at the same energy level
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orbital energy diagrams
in multielectron atoms, various subshells of aprincipal shell are at different energy levels,but all orbitals within a subshell are at the
same energy level
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orbital energy diagrams
orbital energies depend on nand l, but not onml
lower nand lvalues = lower energies
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electron configurations
the way electrons are distributed among thevarious orbitals in the atom is called theelectron configurationof the atom
how we fill in the shells and subshells withelectrons
can be represented using spdf notationororbital diagrams
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electron configurations
example spdf notation
1s2
2s2
2p3
coefficients = n
letters = l superscripts = # of electrons in subshell
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electron configurations
example spdf notation
1s2
2s2
2p3
2 electrons in 1ssubshell
2 electrons in 2ssubshell
3 electrons in 2psubshell
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rules for electronconfigurations
1. electrons occupy orbitals of the lowest availableenergy level
E
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rules for electronconfigurations
1. electrons occupy orbitals of the lowest availableenergy level
1s, 2s, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s
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rules for electronconfigurations
1. electrons occupy orbitals of the lowest availableenergy level
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rules for electronconfigurations
1. electrons occupy orbitals of the lowest availableenergy level
2. no two electrons in the same atom can have all 4
quantum numbers alike an atomic orbital can accommodate only 2 electrons, and
these electrons must have opposing spins
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rules for electronconfigurations
1. electrons occupy orbitals of the lowest availableenergy level
2. no two electrons in the same atom can have all 4
quantum numbers alike
3. in a group of orbitals of identical energy, electronsenter empty orbitals whenever possible
Hunds rule: 2 electrons carry identical charge and repel
each other, therefore electrons go into unoccupied orbitalsof lowest energy levels first
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aufbau principle
building up
building electron configurations by increasing
atomic number, and thus increasing electrons
ex: He electron configuration is just like H,with one more electron, Li is just like He, with
one more electron we just keep adding electrons using the rules
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in class activity
give the spdfand orbital diagramfor eachof the following atoms:
B F P Ca