Download Electron Configuration of Atoms

Electron
Structure of
the Atom:
Electron
Configuration
7-1
Rxn with O2,
CO2
Density,
MP, BP,
polarity
Such
as
Chemical
Change
Chemical
Property
Such
as
Physical
property
Can be
characterized
by
Such
as
Formation of
H2O, H2, O2
Can undergo
changes
such as
Physical
Change
Such
as
Filtration,
diffusion
MATTER
elements
Solid
Can be converted
through melting into
Can be
described
by KMT
Liquid
Can be in
different
states
such as
Can be
classified
into
Can combine chemically into
compounds
Can combine
physically
into
Can be converted through
evaporation into
Gas
mixtures
Atomic Structural Theories: Thomson
Thomson – plum pudding model
Atomic Structural Theories: Rutherford
Rutherford – nuclear model
Atomic Structural Theories: Bohr
el
Bohr - planetary model
7-5
Atomic Structural Theories: Quantum Model
The Big Question
How is the electron configuration
of an atom written?
7-7
Introductory Experiment
Animation: fireworks
7-8
Orbital Diagrams
• Orbital diagrams
– Show the sublevels and orbitals that can exist at each
principal energy level.
– Each box represents an orbital.
– Groups of boxes represent sublevels.
Figure 7.17
7-9
Orbital Diagram: Hydrogen Atom
In the hydrogen atom only, the sublevels within a principal
energy level all have the same energy.
Each box represents an orbital.
7-10
Orbital Diagram: Multielectron Atom
• In multielectron atoms,
the sublevels within a
principal energy level
have different energies.
• Sublevels within a
principal energy level
split so that
–s<p< d<f
Figure 7.18
7-11
Orbital Diagram Rules
• Two principles and one rule determine how the
electrons are filled in the principal energy levels
and sublevels.
• Electrons are always filled in their ground state,
or lowest energy state.
7-12
Orbital Diagram Rules
Aufbau principle:
Electrons fill orbitals starting with the lowestenergy orbitals.
Pauli exclusion principle:
A maximum of two electrons can occupy each
orbital, and they must have opposite spins.
Hund’s rule:
Electrons are distributed into orbitals of
identical energy (same sublevel) in such a
way as to give the maximum number of
unpaired electrons.
7-13
Orbital Diagrams
Electrons
are
represented
by up and
down
arrows.
7-14
Orbital Diagrams
• Electrons occupy the lowest-energy orbitals first
(aufbau principle).
• No more than two electrons occupy each orbital
(Pauli exclusion principle).
Two electrons in the same
orbital must have opposite
spins, represented by the up
and down arrows.
7-15
Orbital Diagram: Helium
7-16
Orbital Diagram: Lithium
7-17
Orbital Diagram: Boron
7-18
Orbital Diagram: Carbon
• Why do the electrons in the p sublevel occupy
separate orbitals?
It takes a little bit of
energy to pair up
electrons, so single
electrons occupy
different orbitals of
the same energy
(Hund’s Rule)
7-19
Orbital Diagram: Carbon
7-20
Electron Configurations
• Shorthand notation which shows the distribution of
electrons among sublevels
7-21
Electron Configurations
Electron
configurations:
Allow us to
represent the
arrangement of the
electrons in an atom.
7-22
Electron Configuration
7-23
Electron
Configurations
For elements in
periods 1 and 2:
Figure 7.19
7-24
Problem
• Use an orbital diagram to
write the electron
configuration for silicon:
Figure 7.18
7-25
Pneumonic device for electron
configurations
The periodic
table provides a
simpler device
for figuring out
electron
configurations.
7-26
Periodicity of Electron Configurations
• Consider the alkali metals:
Li
Na
K
Rb
1s22s1
1s22s22p63s1
1s22s22p63s23p64s1
1s22s22p63s23p64s23d104p65s1
– Can you see a pattern? Consider some more
examples and look for patterns.
7-27
Periodicity of Electron Configurations
• Consider the alkaline earth metals:
Be
Mg
Ca
Sr
1s22s2
1s22s22p63s2
1s22s22p63s23p64s2
1s22s22p63s23p64s23d104p65s2
7-28
Periodicity of Electron Configurations
• Consider a few of the halogens:
F
Cl
Br
1s22s22p5
1s22s22p63s23p5
1s22s22p63s23p64s23d104p5
7-29
Periodicity of Electron Configurations
• Consider some of the noble gases:
Ne
Ar
Kr
1s22s22p6
1s22s22p63s23p6
1s22s22p63s23p64s23d104p6
7-30
Conclusion
Electron configuration
and
periodic table placement?
7-31
Periodicity of Electron Configurations
• Notice that the number of columns in the s,
p, d, and f blocks is the same as the number
of electrons allowed in each sublevel.
• This allows us to use the periodic table to
write electron configurations without the
aid of an orbital diagram.
7-32
Periodicity of Electron Configurations
The periodic table can be used to fill orbital
diagrams or to find electron configurations.
Figure 7.20
7-33
Periodicity of Electron Configurations
• The principal energy level number, the
number that comes before the sublevel
letter designation, is the same as the period
number for the s and p sublevels.
• For the d sublevels, the principal energy
level number is one less than the period
number. Why?
7-34
7-35
Periodicity of Electron Configurations
The relation between orbital filling and the periodic table
7-36
Periodicity of Electron Configurations
Figure 7.21
7-37
Problem: electron configuration for
phosphorus
7-38
Problem: electron configuration for
phosphorus
2
1s
Orbital Diagram: Carbon
2
2s
6
2p
2
3s
3
3p
7-39
Write the electron configuration for
manganese:
Figure 7.22
7-40
Problem: electron configuration for
manganese
2
1s
2
2s
6
2
6
Diagram:3p
Carbon
2pOrbital3s
2
5
4s 3d
7-41
Worksheet #2-1
Electron Configuration I:
Draw the electron configuration (long form)
of the following elements just by looking at
the periodic table.
Na
S
Eu
Ba
F
Ga
Ar
Sn
Pb
Mo
U
7-42
Condensed Electron Configurations
Abbreviated electron configurations are often used for
elements with many electrons.
Notice that iron’s electron configuration starts out with
argon’s electron configuration, but ends differently:
Fe
Ar
1s22s22p63s23p64s23d6
1s22s22p63s23p6
We use the symbol [Ar] to represent argon’s electron
configuration:
Fe
[Ar] 4s23d6
7-43
Periodicity of Electron Configurations
7-44
Periodicity of Electron Configurations
7-45
Figure 7.23
7-46
Worksheet #2- 2
Electron Configuration II:
Draw the electron configuration (condensed
form) of the following elements just by
looking at the periodic table.
Na
S
Eu
Ba
F
Ga
Ar
Sn
Pb
Mo
U
Valence Electrons for the Main-Group
Elements
• The last filled principal energy level is called the
valence level, or valence shell.
• The valence level contains electrons that are highest
in energy and occupy orbitals that extend further
from the nucleus than those in the lower levels.
• Valence electrons occupy orbitals in the valence
level. All the other electrons are called core
electrons, or inner electrons.
7-48
Sample Problem: Valence Electrons
• How many valence electrons in bromine?
Br
1s22s22p63s23p64s23d104p5
Bromine has 7 valence electrons (4s and 4p).
7-49
Sample Problem : Valence Electrons
• How many valence electrons in Calcium?
Ca
1s22s22p63s23p64s2
Calcium has 2 valence electrons (4s).
7-50
Sample Problem: Valence Electrons
Determine the number of valence electrons in
each of the following:
a)
b)
c)
d)
e)
f)
F
Li
Na
C
Si
Pb
7
1
1
4
4
4
7-51
Conclusion
Electronic configuration?
Valence electron?
Family Number?
7-52
Conclusion
The valence electrons of family A elements
are the same as the family number. They
can be seen in the outer most energy levels
in the electron configuration of the
element.
The same is not true for family B elements.
Electron Configurations for Ions
• In atoms, the number of electrons is equal to the
number of protons, which is the atomic number.
• In ions, the number of electrons does not equal the
atomic number. We must add or subtract electrons,
depending on whether the ion is an anion or cation.
7-54
Electron Configurations for Ions
Write the electron configuration for Na+:
Na = 1s22s22p63s1
Na+ has a positive charge of 1; therefore, we need to
subtract 1 electron from the total number of
electrons, 11.
Na+ has 10 electrons and is iso-electronic with Ne.
1s22s22p6
7-55
Electron Configurations for Ions
Write the electron configuration for Cl-:
Cl = 1s22s22p63s23p5
Cl- has a negative charge of 1; therefore, we need to add
1 electron from the total number of electrons, 17.
Cl- has 18 electrons and is iso-electronic with Ar.
1s22s22p63s23p6
7-56
Worksheet #2-3
Electron Configuration of Ions:
Write the electron configuration in condensed notation of the following ions.
Ion
BrN3K+
Sr2+
S2P3Ni2+
Al3+
Fe2+
Fe3+
Electron configuration Electron configuration Isoelectronic
(condensed form) of the of the ion (condensed
with
neutral atom
form)
7-57
Conclusion
Electron configuration of ions?
Family number?
Isoelectronic with?
7-58
Conclusion
Family A atoms form ions so as to have the
same electron configuration as a noble gas
element.
The charges of the ions formed can be
determined from the family number of the
element.
Conclusion
For family B metals, the electrons lost in ion
formation come from the highest energy
level filled (not the d-electrons yet)
Quantum Numbers
Each electron has its own set of four quantum
numbers.
These quantum numbers describe the location
and the shape of the electron’s orbital.
Quantum Numbers
Quantum Numbers and Atomic Orbitals
An atomic orbital is specified by four quantum numbers.
n the principal quantum number - a positive integer
l the angular momentum quantum number - an integer from 0 to n-1
ml the magnetic moment quantum number - an integer from -l to +l
ms the magnetic spin quantum number = -1/2 and + 1/2
Quantum Numbers
Summary of Quantum Numbers of Electrons in Atoms
Name
Symbol
Permitted Values
Property
principal
n
positive integers(1,2,3,…)
orbital energy (size)
angular
momentum
l
integers from 0 to n-1
orbital shape ( l = 0, 1, 2, and
3 correspond to s, p, d, and f
orbitals, respectively.)
magnetic
ml
integers from -l to 0 to +l
orbital orientation
spin
ms
+1/2 or -1/2
direction of e- spin
7-63
Quantum Numbers
Table 7.2 The Hierarchy of Quantum Numbers for Atomic Orbitals
Name, Symbol
(Property)
Allowed Values
Quantum Numbers
Principal, n
Positive integer
(size, energy)
(1, 2, 3, ...)
1
Angular
0 to n-1
momentum, l
(shape)
0
0
0
0
Magnetic, ml
-l,…,0,…,+l
(orientation)
2
3
1
0
1
2
0
-1
0 +1
-1
-2
0 +1
-1
0
+1 +2
Quantum Numbers
• Where can you find Donna?
• Donna lives in a dorm in a condominium unit. In the dorm
floor, there are male and female sections per floor. Per room,
there are two beds only: one near the window, one not. If she
is asked, where EXACTLY she lives/sleeps, how would she
answer?
Prince David Condominium in Katipunan Ave
At the 3rd floor
Female section
Room 314
Bed near window
7-65
Quantum Numbers
• Where can you find the electron?
• The quantum mechanical model uses a
certain way to describe an orbital. You can
say you are asking the question, Where does
my electron live/reside?
We use three quantum numbers to describe an orbital. We
add a fourth to pinpoint the electron in that orbital
1.
2.
3.
4.
Principal quantum no. (n)
Azimuthal or Angular Momentum quantum no. (l)
Magnetic quantum no. (ml)
Spin quantum no. (ms)
7-66
Quantum Numbers
Prince David Condominium in
Katipunan Ave
The electron belongs to Chlorine
At the 3rd floor
At the 3rd energy level (n=3)
Female section
In the p-subshell (l=1)
Room 314
Bed near window
In one of the three
degenerate orbitals
eg. ml= 0
Electron is spin-up
eg. ms= +1/2
7-67
Sample Problem
What are the quantum numbers of a 1s1 electron?
Answer:
n=1
l=0
ml = 0
ms = -1/2
Sample Problem
What are the quantum numbers of a 3p2 electron?
Answer:
n=3
l=1
ml = 0
ms = -1/2
Sample Problem
What are the quantum numbers of a 5d7 electron?
Answer:
n=5
l=2
ml = -1
ms = + 1/2
Worksheet #2-4
Electron Quantum Numbers:
Write the quantum numbers of the following electrons.
electrons
n
l
ml
ms
2s1
3p5
3d3
4d7
4f4
7-71
Summary of Electron Configuration Concepts
1.
2.
3.
4.
5.
6.
Long form
Condensed form
Ions, iso-electronic, family A and B elements
Family Number/Period Number
Valence electrons
Quantum numbers
Points to Ponder…..
• Is there a proton configuration or a neutron
configuration? Why or why not?
• How do scientists synthesize new elements?
• What are the newest four elements added to
the periodic table?
• Is there a limit to the number of elements
that scientists can synthesize?