Electron Spin Quantum Number
1
Diamagnetic: NOT attracted to a magnetic
field
field-- all electrons are paired
Paramagnetic: substance is attracted to a
magnetic field. Substance has unpaired
electrons..
electrons
2
3 Rules for Filling Electrons
• Aufbau Principle – lowest energy to
highest energy-regardless of numbers
• Hund’s Rule – one electron goes in
each orbital before two go in any
• Pauli’s Exclusion Principle – no two
electrons can have the same exact set
of 4 quantum numbers – one goes up
and the other goes down
Electron Configurations
3
• After Aufbau came the most modern way of
assigning electrons.
• This way is done by using a number, letter
and superscript number.
• For example 3s2
• The first number is the same as “n” in
quantum numbers.
• The letter is the conversion of l, when 0,1,2,3
equals s, p, d, f
• The last superscript number is the
combination of ml and s.
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4
The Periodic Table is a Map
• The periodic table is a map to the
electron configurations.
• It is arranged by the AUFBAU principle.
• For example Let’s Write the Electron
Configuration for Arsenic by Using
only the table…
5
Electron
Filling
Order
6
Writing Atomic Electron
Configurations
Two ways of
writing configs.
One is called
the spdf
notation.
spdf notation
for H, atomic number = 1
1
1s
value of n
no. of
electrons
value of l
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7
Electron Configurations
and the Periodic Table
Figure 8.7
8
Configuration of Arsenic
• Go from 1-33
• 1s22s22p63s23p64s23d104p3
9
Writing Atomic Electron
Configurations
Two ways of
writing
configs. Other
is called the
orbital box
notation.
ORBITAL BOX NOTATION
for He, atomic number = 2
2
1s
1s
Arrows
depict
electron
spin
One electron has n = 1, l = 0, ml = 0, ms = + 1/2
Other electron has n = 1, l = 0, ml = 0, ms = - 1/2
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10
11
Another Way of Showing
electron Configuration is
through the use of arrows.
• The orbitals are shown as boxes (or
blanks)
• The electrons are shown as arrows (up
or down is one electron)
• When an orbital is complete, 2
opposite arrows are shown
• One must go in each before 2 in
any(equal sublevel) ,and a sublevel
must be complete before you go to the
next.
12
Lithium
Group 1A
Atomic number = 3
1s22s1 --->
---> 3 total electrons
3p
3s
2p
2s
1s
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Boron
3p
13
Group 3A
Atomic number = 5
1s2 2s2 2p1 --->
--->
5 total electrons
3s
2p
2s
1s
14
Carbon
Group 4A
Atomic number = 6
1s2 2s2 2p2 --->
--->
6 total electrons
3p
Here we see for the first time
HUND’S RULE. When
placing electrons in a set of
orbitals having the same
energy, we place them singly
as long as possible.
3s
2p
2s
1s
15
Nitrogen
3p
Group 5A
Atomic number = 7
1s2 2s2 2p3 --->
--->
7 total electrons
3s
2p
2s
1s
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16
Neon
Group 8A
Atomic number = 10
1s2 2s2 2p6 --->
--->
10 total electrons
3p
3s
2p
2s
Note that we have
reached the end of
the 2nd period, and
the 2nd shell is full!
1s
17
Aluminum
Group 3A
Atomic number = 13
1s2 2s2 2p6 3s2 3p1
[Ne] 3s2 3p1
3p
All Group 3A elements
have [core] ns2 np1
configurations where n
is the period number.
3s
2p
2s
1s
18
Phosphorus
Group 5A
Atomic number = 15
1s2 2s2 2p6 3s2 3p3
[Ne] 3s2 3p3
All Group 5A elements
have [core ] ns2 np3
configurations where n
is the period number.
3p
3s
2p
2s
1s
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19
A Glitch?
•
•
•
•
•
Write the noble gas configuration for 61Pm.
[Xe] 6s2 5d1 4f4
Write the noble gas configuration for 74W.
[Xe] 6s2 5d4 4f14
When the element ends in “d” add the one to
the other “d” electrons
• When the element ends in in “f” show the d1
electron.
Ion Configurations
20
To form anions from elements add 1
or more ee- to subshell of highest n
[or highest (n + l)].
P [Ne] 3s2 3p3 + 3e3e- ----->
>
3
2
6
P [Ne] 3s 3p
Ion Configurations
21
To form cations from elements remove 1 or
more ee- from subshell of highest n [or
highest (n + l)].
Al [Ne] 3s2 3p1 - 3e3e- ----->
> Al3+ [Ne]
3p
3p
3s
3s
2p
2p
2s
2s
1s
1s
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Ion Configurations
For transition metals, remove ns electrons and
then (n - 1) electrons.
Fe [Ar] 4s2 3d6
loses 3 electrons --->
---> Fe3+ [Ar] 3d5
23
Ion Configurations
For transition metals, remove ns electrons and
then (n - 1) electrons.
Fe [Ar] 4s2 3d6
loses 2 electrons --->
---> Fe+2 [Ar] 3d6
Fe2+
Fe
4s
3d
4s
3d
24
Ion Configurations
For transition metals, remove ns electrons and
then (n - 1) electrons.
Fe [Ar] 4s2 3d6
loses 2 electrons --->
---> Fe2+ [Ar] 3d6
Fe2+
Fe
4s
3d
4s
3d
Fe3+
4s
3d
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What about excited electrons?
• When an electron is excited,
remember it jumps to a higher
energy level.
• Na 1s2 2s2 2p6 3s1
• Na* excited may look like this
1s2 2s2 2p5 3s2
• Add the electrons up to get the
atomic number- look for jumping
electrons!
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