chapter 4b_electronic atomic structure
TRANSCRIPT
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CHAPTER4
Electronic Structure ofAtom
Electron ConfigurationElectron Configuration
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SummarySummary
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Indicates main energy levels
n = 1, 2, 3, 4
Each main energy level has sub-levels
Principal Quantum Number, nPrincipal Quantum Number, n
Energy SublevelsEnergy Sublevels
s p d f g
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The principle quantum number, n, determinesthe number of sublevels within the principleenergy level.
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Orbital Quantum Number, Orbital Quantum Number, (Angular Momentum Quantum Number)(Angular Momentum Quantum Number)
Indicates shape of orbital sublevels
= n-1 sublevel
0 s
1 p
2 d
3 f
4 g
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OrbitalOrbital
The space where there is a high
probability that it is occupied bya pair of electrons.
Orbitals are solutions ofSchrodingers equations.
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Orbitals in SublevelsOrbitals in Sublevels
Sublevel # Orbitals # electrons
s 1 2
p 3 6
d 5 10
f 7 14
g 9 18
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Shell electrons with the same value ofn
Subshell electrons with the same values ofnandl
Orbital electrons with the same values ofn, l, andml
How many electrons can an orbital hold?
Ifn, l, and mlare fixed, then m
s= or -
= (n, l, ml, )or = (n, l, ml, -)
An orbital can hold 2 electrons 7.6
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How many 2p orbitals are there in an atom?
2p
n=2
l = 1
Ifl = 1, then ml = -1, 0, or +1
3 orbitals
How many electrons can be placed in the 3d subshell?
3d
n=3
l = 2
Ifl = 2, then ml = -2, -1, 0, +1, or +2
5 orbitals which can hold a total of 10 e-
7.6
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9
Electron ConfigurationElectron Configuration
The way electrons are arrangedaround the nucleus.
Three rules are used to build theelectron configuration:
Aufbaus principle
Pauli Exclusion Principle
Hunds Rule
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Aufbaus PrincipleAufbaus Principle
Electrons occupy orbitals of lower energy first.
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Diagram
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nergy of orbitals in anergy of orbitals in a singlesingle electron atomelectron atomEnergy only depends on principal quantum number n
En = -RH( )1
n2
n=1
n=2
n=3
7.7
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Energy of orbitals in a multi-electron atom
Energy depends on n and l
n=1 l = 0
n=2 l = 0n=2 l = 1
n=3 l = 0n=3 l = 1
n=3 l = 2
7.7
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Fill up electrons in lowest energy orbitals (Aufbau principle)
H 1 electron
H 1s1
He 2 electrons
He 1s2
Li 3 electrons
Li 1s22s1
Be 4 electrons
Be 1s22s2
B 5 electrons
B 1s22s22p1
C 6 electrons
? ?
7.7
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Pauli Exclusion Principle(Wolfgang Pauli, Austria, 1900-1958)
-Electron Spin Quantum Number
An orbital can hold only two electronsand they must have opposite spin.
Electron Spin Quantum Number (ms):
+1/2, -1/2
uli exclusion principle - no two electrons in an atocan have the same four quantum numbers.
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Hunds Rule
In a set of orbitals, the electrons will fillthe orbitals in a way that would givethe maximum number of parallel spins
(maximum number of unpairedelectrons).
Analogy: Students could fill each seatof a school bus, one person at a time,before doubling up.
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Aufbau
DiagramforHydrogen
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Aufbau
Diagramfor
Helium
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AufbauDiagram
forLithium
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Aufbau
Diagramfor Boron
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AufbauDiagram
forCarbon
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d f bi l (filli ) i l i l
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Order of orbitals (filling) in multi-electron atom
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
7.7
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Notations of ElectronNotations of Electron
ConfigurationsConfigurations
Standard
Shorthand
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AufbauDiagram
forFluorine
Standard Notation
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Standard Notation
of Fluorine
MainE
nergy
Level
Numbers
1,2,2 Sublevels
Number of electrons
in the sub level 2,2,5
1s2 2s2 2p5
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Shorthand Notation
Use the last noble gas that islocated in the periodic table rightbefore the element.
Write the symbol of the noble gasin brackets.
Write the remaining configuration
after the brackets.Ex: Fluorine: [He] 2s2 2p5
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8.2
Periodic Table
O b h ll b i fill d i h l
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Outermost subshell being filled with electrOutermost subshell being filled with electr
7.8
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Paramagnetic
unpaired electrons
2p
Diamagnetic
all electrons paired
2p
7.8
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C 6 electrons
The most stable arrangement ofelectrons in subshells is the one with
the greatest number of parallel spins(Hunds rule).
C 1s22s22p2
N 7 electrons
N 1s22s22p3
O 8 electrons
O 1s22s22p4
F 9 electrons
F 1s22s22p5
Ne 10 electrons
Ne 1s22s22p6
7.7
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What is the electron configuration of Mg?
Mg 12 electrons
1s < 2s < 2p < 3s < 3p < 4s
1s22s22p63s2 2 + 2 + 6 + 2 = 12 electrons
7.7
Abbreviated as [Ne]3s2 [Ne] 1s22s22p6
What are the possible quantum numbers for the last(outermost) electron in Cl?
Cl 17 electrons 1s < 2s < 2p < 3s < 3p < 4s
1s22s22p63s23p5 2 + 2 + 6 + 2 + 5 = 17 electrons
Last electron added to 3p orbital
n = 3 l = 1 ml
= -1, 0, or +1 ms
= or -
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