Aproksimasi Orbital Atom Berelektron Banyak
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Transcript of Aproksimasi Orbital Atom Berelektron Banyak
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Aproksimasi orbital atom
berelektron banyak Outline:
Spin
The Aufbau Principle
Filling up orbitals and the Periodic Table
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Spin
Further experimentsdemonstrated the needfor one more quantumnumber.
Specifically, some
particles (electrons inparticular)demonstrated inherentangular momentum.
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Spin (cont.)
The new quantumnumber is ms
(analogous to ml).
For the electron, ms
has two values:
+1/2 and -1/2
ms= 1/2
ms= -1/2
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The Aufbau Principal
For polyelectronic atoms, a direct solution of theSchrodinger Eq. is not possible.
When we construct polyelectronic atoms, we usethe hydrogen-atom orbital nomenclature to discussin which orbitals the electrons reside.
This is an approximation (and it is surprising howwell it actually works).
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The Aufbau Principal (cont.)
When placing electrons into orbitals in theconstruction of polyelectronic atoms, we use theAufbau Principle.
This principle states that in addition to addingprotons and neutrons to the nucleus, one simplyadds electrons to the hydrogen-like atomic orbitals
Pauli exclusion principle: No two electrons mayhave the same quantum numbers. Therefore, onlytwo electrons can reside in an orbital
(differentiated by ms).
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The Aufbau Principal (cont.)
Finally, orbitals are filled starting from the lowestenergy.
Example: Hydrogen
1s 2s 2p
Example: Helium (Z = 2)
1s 2s 2p
1s1
1s2
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The Aufbau Principal (cont.) Lithium (Z = 3)
1s 2s 2p
1s 2s 2p
Berillium (Z = 4)
Boron (Z = 5)
1s 2s 2p
1s22s1
1s22s2
1s22s22p1
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The Aufbau Principal (cont.) Carbon (Z = 6)
1s 2s 2p
1s 2s 2p
Nitrogen (Z = 7)
Hunds Rule: Lowest energy configuration is
the one in which the maximum number of unpaired electrons
are distributed amongst a set of degenerate orbitals.
1s22s22p2
1s22s22p3
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The Aufbau Principal (cont.) Oxygen (Z = 8)
1s 2s 2p
1s 2s 2p
Fluorine (Z = 9)
1s22s22p4
1s22s22p5
1s 2s 2p
Neon (Z = 10)
1s22s22p6
full
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The Aufbau Principal (cont.)
Sodium (Z = 11)
3s
1s22s22p63s1
3s 3p
Argon (Z = 18)
[Ne]3s23p6
Ne [Ne]3s1
Ne
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Suppose there are four possible spin values instead of
two. In this case, what would be the electron
configuration of Cl?
A. 1s42s42p9
B. 1s22s22p63s23p5
C. 1s3
2s3
2p9
3s2
D. 1s62s62p5
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Which of the following electron configuration
represents an excited state of N?
A. 1s22s22p3
B. 1s22s22p23s1
C. 1s22s32p2
D. 1s22s22p2
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The Aufbau Principal (cont.)
We now have the orbital configurations for the first 18 elements.
Elements in same column have the same # of valence electrons!
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The Aufbau Principal (cont.)
Similar to Sodium, we begin the next row of the periodic
table by adding electrons to the 4s orbital.
Why not 3d before 4s? 3d is closer to the nucleus
4s allows for closer
approach; therefore, is energetically preferred.
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The Aufbau Principal (cont.)
Elements Z=19 and Z= 20:
Z= 19, Potassium: 1s22s22p63s23p64s1 = [Ar]4s1
Z= 20, Calcuim: 1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
= [Ar]4s
2
Elements Z=21to Z=30 have occupied d orbitals:
Z= 21, Scandium: 1s22s22p63s23p64s23d1 = [Ar] 4s23d1
Z= 30, Zinc: 1s22s22p63s23p64s23d10 = [Ar] 4s23d10
Z = 24, Chromium: [Ar] 4s13d5 exception
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The Aufbau Principal (cont.)
This orbital filling scheme gives rise to the modern
periodic table.
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The Aufbau Principal (cont.)
After Lanthanum ([Xe]6s25d1), we start filling 4f.
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The Aufbau Principal (cont.)
After Actinium ([Rn]7s26d1), we start filling 5f.
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What is the electron configuration for the indicated element?
A. 1s22s22p63s23p64s23d3
C. 1s22s22p63s23p64s23d2
B. 1s22s22p63s23p64s24d3
D. 1s22s22p73s23p64s23d2
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The Aufbau Principal (cont.)
Heading on column given total number of valence
electrons.
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The Aufbau Principal (cont.)
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Summary
Electrons go into
hydrogen-like orbitals
to constructpolyelectronic atoms.
Remember the
adjacent trickfor
remembering how to
fill orbitals.