Hund

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Hunds Rule

• For an atom in its ground-state configuration,
  all unpaired electrons have the same spin
  orientation.
• Therefore electrons tend to occupy all free
  orbitals and not pair up, so that their spins all
  add up to produce a general vector for the atom.

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Fig. 8.5
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Orbital Occupancy for the First 10 Elements, H
through Ne
Fig. 8.6
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Orbital Box Diagrams - II B Ne
B (5 e-) 1s2 2s2 2p1
C (6 e-) 1s2 2s2 2p2
N (7 e-) 1s2 2s2 2p3
O (8 e-) 1s2 2s2 2p4
F (9 e-) 1s2 2s2 2p5
Ne (10 e-) 1s2 2s2 2p6
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Quantum Numbers Noble Gases
Electron Orbitals
Number of Electrons Element
1s2
2
He
1s2 2s22p6
10
Ne
1s2 2s22p6 3s23p6
18 Ar
1s2 2s22p6 3s23p6 4s23d104p6
36 Kr
1s2 2s22p6 3s23p6 4s23d104p6 5s24d105p6
54 Xe
1s2 2s22p6 3s23p6 4s23d104p6 5s24d105p6
6s24f14 5d106p6 86 Rn
1s2 2s22p6 3s23p6 4s23d104p6 5s24d105p6
6s24f145d106p6 7s25f146d10?
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Figure 8.8 Orbital energies for the scandium
atom (Z21).
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The Periodic Table of the Elements
Electronic Structure
He
H
Ne
F
O
N
C
B
Li
Be
Ar
Cl
S
P
Si
Al
Na
Mg
Kr
Zn
Cu
Ni
Co
Fe
Mn
Cr
V
Ti
Sc
Br
Se
As
Ge
Ga
K
Ca
Xe
Cd
Ag
Pd
Rh
Ru
Tc
Mo
Nb
Zr
Y
I
Te
Sb
Sn
In
Rb
Sr
Rn
Hg
Au
Pt
Ir
Os
Re
W
Ta
Hf
La
At
Po
Bi
Pb
Tl
Cs
Ba
Ac
Rf
Ha
Fr
Ra
Sg
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
S Orbitals
P Orbitals f Orbitals
d Orbitals
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Figure 8.12 A periodic table illustrating the
building-up order.
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Figure 8.7 A mnemonic diagram for the
building-up order (diagonal rule).
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Valence and Core Electrons

• Valence Electrons - Those electrons outside of a
  closed electron shell. These electrons take part
  in chemical reactions.
• Core Electrons - The electrons in the closed
  shells. They cannot take part in chemical
  reactions.
• Sodium 11 electrons
• Valence electrons Ne 3s 1 --- one
• Core electrons 1s 2 2s 2 2p 6 ---
  Ten
• Chlorine 17 electrons
• Valence electrons Ne 3s 2 3p 5----
  seven
• Core 2 2s 2 2p 6 ---- Ten

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Condensed Ground-State Electron
Configurations in the First Three Periods
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Orbital Box Diagrams - III Na
Ar
Atomic Number Orbital Box
Condensed Electron Element
Diagrams(3s3p)
Configuration
11 Na
He 3s1 12
Mg
He 3s2 13 Al

He 3s23p1 14 Si

He 3s23p2 15 P

He 3s23p3 16 S

He 3s23p4 17 Cl

He 3s23p5 18 Ar

He 3s23p6
3s
3px
3py
3pz
3s
3px
3py
3pz
3s
3px
3py
3pz
3s
3py
3px
3pz
3s
3py
3px
3pz
3s
3py
3px
3pz
3py
3px
3pz
3s
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Figure 8.9 A periodic table.
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Figure 8.14 Mendeleevs periodic table.
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Figure 8.17 Representation of atomic radii
(covalent radii) of the main-group elements.
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Atomic Radii of the Main-Group and Transition
Elements
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Electronic Configuration Ions

• Na 1s 2 2s 2 2p 6 3s 1 Na 1s 2
  2s 2 2p 6
• Mg 1s 2 2s 2 2p 6 3s 2 Mg2 1s 2 2s
  2 2p6
• Al 1s 2 2s 2 2p 6 3s 2 3p 1 Al3 1s 2
  2s 2 2p 6
• O 1s 2 2s 2 2p 4 O- 2 1s
  2 2s 2 2p 6
• F 1s 2 2s 2 2p 5 F- 1
  1s 2 2s 2 2p 6
• N 1s 2 2s 2 2p 3
  N- 3 1s 2 2s 2 2p 6

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Isoelectronic Atoms and Ions

• H- 1 He Li Be2
• N- 3 O- 2 F- Ne Na Mg2
  Al3
• P- 3 S- 2 Cl- Ar K Ca2
  Sc3 Ti4
• As- 3 Se- 2 Br- Kr Rb Sr2
  Y3 Zr4
• Sb- 3 Te- 2 I- Xe Cs Ba2
  La3 Hf4

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Pseudo - Noble Gas Electron Configurations
Elements in groups 3A, 4A, and 5A can form
cations by losing enough electrons to leave a
pseudo noble gas configuration. By losing
electrons and leaving a filled d orbital, which
is quite stable!
Sn Kr 5s24d105p2
Sn4 Kr 4d10 4 e - Sn Kr 5s24d105p2
Sn2 Kr 5s24d10
2 e - Pb Xe 4f145d106s26p2
Pb2 Xe 4f145d106s2 2 e- Pb Xe
4f145d106s26p2 Pb4 Xe
4f145d10 4 e- As Ar 3d104s24p3
As3 Ar 3d104s2 3
e- As Ar 3d104s24p3
As5 Ar 3d10 5 e- Sb Kr 4d105s25p3
Sb3 Kr
4d105s2 3 e- Sb Kr 4d105s25p3
Sb5 Kr 4d10 5 e-
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Ranking Ions According to Size
Problem Rank each set of Ions in order of
increasing size. a) K, Rb, Na b) Na,
O2-, F - c) Fe2, Fe3 Plan We find the
position of each element in the periodic table
and apply the ideas of size i) size increases
down a group, ii) size decreases across a period
but increases from cation to anion. iii) size
decreases with increasing positive (or
decreasing negative) charge in an isoelectronic
series. iv) cations of the same element decreases
in size as the charge increases. Solution a)
since K, Rb, and Na are from the same group
(1A), they increase in size down the
group Na lt K lt Rb b) the ions Na, O2-,
and F- are isoelectronic. O2- has lower Zeff than
F-, so it is larger. Na is a cation, and
has the highest Zeff, so it is smaller
Na lt F- lt O2- c) Fe2 has a lower charge than
Fe3, so it is larger Fe3 lt Fe2
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Ranking Ions According to Size
Problem Rank each set of Ions in order of
increasing size. a) K, Rb, Na b) Na,
O2-, F - c) Fe2, Fe3 Plan We find the
position of each element in the periodic table
and apply the ideas of size i) size increases
down a group, ii) size decreases across a period
but increases from cation to anion. iii) size
decreases with increasing positive (or
decreasing negative) charge in an isoelectronic
series. iv) cations of the same element decreases
in size as the charge increases. Solution a)
since K, Rb, and Na are from the same group
(1A), they increase in size down the
group Na lt K lt Rb b) the ions Na, O2-,
and F- are isoelectronic. O2- has lower Zeff than
F-, so it is larger. Na is a cation, and
has the highest Zeff, so it is smaller
Na lt F- lt O2- c) Fe2 has a lower charge than
Fe3, so it is larger Fe3 lt Fe2
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Periodicity of First Ionization Energy (IE1)
Like Figure 8-18
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Fig. 8.15
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Identifying Elements by Its Successive
Ionization Energies
Problem Given the following series of
ionization energies (in kJ/mol)
for an element in period 3, name the element and
write its electron
configuration
IE1 IE2 IE3
IE4 580
1,815 2,740
11,600 Plan Examine the values to find the
largest jump in ionization energy,
which occurs after all valence electrons have
been removed. Use the periodic
table! Solution
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Identifying Elements by Its Successive
Ionization Energies
Problem Given the following series of
ionization energies (in kJ/mol)
for an element in period 3, name the element and
write its electron
configuration
IE1 IE2 IE3
IE4 580
1,815 2,740
11,600 Plan Examine the values to find the
largest jump in ionization energy,
which occurs after all valence electrons have
been removed. Use the periodic
table! Solution
The largest jump in IE occurs after IE3 so the
element has 3 valence electrons thus it is
Aluminum ( Al, Z13), its electron configuration
is
1s2 2s2 2p6 3s2 3p1
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Fig. 8.16
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Ranking Elements by First Ionization Energy
Problem Using the Periodic table only, rank the
following elements in each
of the following sets in order of increasing
IE! a) Ar, Ne, Rn b) At, Bi, Po c)
Be, Na, Mg d) Cl, K, Ar Plan Find their
relative positions in the periodic table and
apply trends! Solution
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Ranking Elements by First Ionization Energy
Problem Using the Periodic table only, rank the
following elements in each
of the following sets in order of increasing
IE! a) Ar, Ne, Rn b) At, Bi, Po c)
Be, Na, Mg d) Cl, K, Ar Plan Find their
relative positions in the periodic table and
apply trends! Solution
a) Rn, Ar,Ne These elements are all noble
gases and their IE
decreases as you go down the group.