Quantum Numbers Describes the arrangement of electrons in atoms in terms of: energy levels, size...
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Transcript of Quantum Numbers Describes the arrangement of electrons in atoms in terms of: energy levels, size...
Quantum Numbers
Describes the arrangement of electrons in atoms in terms of:energy levels, sizePathway of travelDirection of rotation
Principal Quantum number (n)
Contain electrons that are similar in
energy and distance from nucleus
Low energy electrons are closest to the
nucleus
Identify by numbers 1, 2, 3, 4, 5, 6…..
The first shell (1) is lowest in energy, 2nd
level next and so on 1<2<3<4
Number of Electrons
Maximum number of electrons in any electron energy level = 2n2
n =1 2(1)2 = 2
n =2 2(2)2 = 8
n =3 2(3)2 = 18
Orbital Quantum number
Indicates the pathway of travel
Electrons move in different paths
due to their negative charge.
Designated s, p, d, f ..
Sublevel energy: s<p<d<f
1 s orbital for every energy level
Spherical shaped
Each s orbital can hold 2 electrons Called the 1s 2s 3s etc..
orbitals.
S orbitals
Spin Quantum number Describes rotation of electron in an
orbital Either clockwise (+1/2) or Counter clockwise (-1/2)
Summary Seven energy levels (n=1,2,3,4…) Four pathways (s,p,d,f) Orientations: s=1, p=3, d=5, f=7 Two spins in each orbital Maximum electrons are: s=2, p=6,
d=10, f=14
Summary
s
p
d
f
# of shapes/orbitals
Max # electrons/orbital
Starts at energy level
1 2 1
3 6 2
5 10 3
7 14 4
By Energy Level First Energy Level only s orbital only 2 electrons 1s2
Second Energy Level
s and p orbitals are available
2 in s, 6 in p 2s22p6
8 total electrons
By Energy Level Third energy level s, p, and d
orbitals 2 in s, 6 in p, and
10 in d 3s23p63d10
18 total electrons
Fourth energy level
s,p,d, and f orbitals
2 in s, 6 in p, 10 in d, ahd 14 in f
4s24p64d104f14
32 total electrons
By Energy Level Any more than
the fourth and not all the orbitals will fill up.
You simply run out of electrons
The orbitals do not fill up in a neat order.
The energy levels overlap
Lowest energy fill first.
Electrons Allowed
All electrons in the same sublevel have the same energy.
All 2s electrons have the same energy. All 2p electrons, the same energy which is slightly higher than that of the 2s electrons
s sublevel 2 electrons
p sublevel 6 electrons
d sublevel 10 electrons
f sublevel 14 electrons
Electron Configurations
List of subshells containing electrons
Written in order of increasing energy
Superscripts give the number of electrons
Electron Configurations The way electrons are arranged in
atoms. Aufbau principle- electrons enter the
lowest energy first. This causes difficulties because of the
overlap of orbitals of different energies. Pauli Exclusion Principle- at most 2
electrons per orbital - different spins
Electron Configuration Hund’s Rule- When electrons occupy
orbitals of equal energy they don’t pair up until they have to .
Let’s determine the electron configuration for Phosporus
Need to account for 15 electrons
The first to electrons go into the 1s orbital
Notice the opposite spins
only 13 more
Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
The next electrons go into the 2s orbital
only 11 more
Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The next electrons go into the 2p orbital
• only 5 more
Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The next electrons go into the 3s orbital
• only 3 more
Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
Incr
easi
ng e
nerg
y
1s
2s
3s
4s
5s6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
7p 6d
4f
5f
• The last three electrons go into the 3p orbitals.
• They each go into seperate shapes
• 3 upaired electrons• 1s22s22p63s23p3
The easy way to remember
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2
• 2 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2
• 4 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
• 12 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2
• 20 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2
• 38 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
• 56 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
4f14 5d10 6p6 7s2
• 88 electrons
Fill from the bottom up following the arrows
1s2s 2p3s 3p 3d4s 4p 4d 4f
5s 5p 5d 5f6s 6p 6d 6f7s 7p 7d 7f
• 1s2 2s2 2p6 3s2
3p6 4s2 3d10 4p6
5s2 4d10 5p6 6s2
4f14 5d10 6p6 7s2
5f14 6d10 7p6 • 108 electrons
Find element on the periodic tableUse the order of filling indicated
across each period
Groups 1-2 = ns level
Groups 3-8 = np level
Transition = (n-1)d level
Lanthanides = (n-2)f level
Periodic Table and Electron Configuration
Orbitals fill in order Lowest energy to higher energy. Adding electrons can change the
energy of the orbital. Half filled orbitals have a lower
energy. Makes them more stable. Changes the filling order
Write these electron configurations
Titanium - 22 electrons 1s22s22p63s23p64s23d2
Vanadium - 23 electrons 1s22s22p63s23p64s23d3
Chromium - 24 electrons 1s22s22p63s23p64s23d4 is expected But this is wrong!!
Chromium is actually 1s22s22p63s23p64s13d5
Why? This gives us two half filled orbitals. Slightly lower in energy. The same principal applies to copper. Write the Cu configuration now
Copper’s electron configuration
Copper has 29 electrons so we expect
1s22s22p63s23p64s23d9
But the actual configuration is 1s22s22p63s23p64s13d10
This gives one filled orbital and one half filled orbital.
Remember these exceptions
Orbital Notation
A 3 dimensional space around a
nucleus in which electrons are most
likely to be found
Shape represents electron density (not
a path the electron follows)
Each orbital can hold up to 2 electrons.
Learning Check S5
A. Number of electrons in a p orbital1) 1e 2) 1e or 2e 3) 3e
B. Number of orbitals in a p subshell1) 1 2) 2 3) 3
C. Number of orbitals in 4d subshell1) 1 2) 3 3) 5
D. Number of electrons (maximum) in a 3d 1) 2e 2) 5e 3) 10e
Solution S5
A. Number of electrons in a p orbital
2) 1e or 2e
B. Number of orbitals in a p subshell
3) 3
C. Number of orbitals in 4d subshell
3) 5
D. Number of electrons in a 3d subshell
3) 10e
The Periodic Law
All the elements in a group have the same electron configuration in their outermost shells
Example: Group 2
Be 2, 2
Mg 2, 8, 2
Ca 2, 2, 8, 2
Learning Check EA5
Specify if each pair has chemical properties that are similar (1) or not (2):
A. Cl and Br
B. 2 - 5 and 2 - 8 - 7
C. 2 - 4 and 2 - 8 - 4
D. P and S
E. O and S
Solution EA5
Specify if each pair has chem. properties that are similar (1) or not similar (2):
A. Cl and Br 1
B. 2 - 5 and 2 - 8 - 7 2
C. 2 - 4 and 2 - 8 - 4 1
D. P and S 2
E. O and S 1
Learning Check S2
Indicate if each configuration is (1) correct or (2) incorrect for potassium. Give an explanation for selection of 1 or 2. Explain
A. 1s22s22p63s1 1 or 2
B. 1s22s22p63s23p6 1 or 2
C. 1s22s22p63s23p64s1 1 or 2
D. 1s22p83s1 1 or 2
E. 1s22s22p63s23p7 1 or 2
Solution E2
For phosphorus, indicate if each configuration is (1) correct or (2) incorrect. Explain why or why not.
A. 2, 2, 8, 5 2
B. 2, 8, 3 2
C. 2, 8, 5 1
D. 2, 6, 7 2
Learning Check S3
Using the periodic table, write the complete electronic configuration for each:
A. Cl
B. Sr
C. I
Solution S3
Using the periodic table, write the complete electronic configuration for each:
A. Cl
1s2 2s2 2p6 3s2 3p5
B. Sr
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
C. I
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5
Learning Check S4
A. The final two notations for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The final three notations for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2