aproksimasi orbital atom berelektron banyak

8/10/2019 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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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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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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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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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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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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This orbital filling scheme gives rise to the modern

periodic table.


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After Lanthanum ([Xe]6s25d1), we start filling 4f.


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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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Heading on column given total number of valence

electrons.


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Summary

Electrons go into

hydrogen-like orbitals

to constructpolyelectronic atoms.

Remember the

adjacent trickfor

remembering how to

fill orbitals.

aproksimasi orbital atom berelektron banyak

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