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Quantum Mechanical Model of the Atom
Progression of Atomic Theory
Bohr Model
• Energy levels
• 1st energy level can hold 2
• 2nd energy level can hold 8
• 3rd energy level can hold 8
• Bohr Model Breaks down after 3rd energy level and no longer applies to Modern Quantum Mechanical Model of the Atom
Bohr Model for Hydrogen• Energy level of an electron
• analogous to the rungs of a ladder
• The electron cannot exist between energy levels, just like you can’t stand between rungs on a ladder
• A quantum of energy is the amount of energy required to move an electron from one energy level to another
• The Bohr model explained the emission spectrum of the hydrogen atom but did not always explain those of other elements.
The Quantum Mechanical Model• In 1926, Erwin Schrodinger
derived an equation with 4quantum numbers that described the energy and position of the electrons in an atom
• The 4 quantum numbers are used in the electron configuration which is a notation using energy levels and sublevels to show how the electrons are distributed within the atom.
Quantum Numbers Chem Saver p 23
11 SS 11
Row # = Energy level or distance
from nucleus
Possibilities 1 –7
7 Rows
Subshell
Possibilities are
s, p, d, or f
4 subshells
# electrons occupying this
orbital
Possibilities are:
s: 1 or 2
p: 1-6
d: 1-10
f: 1-14
Energy Levels and Sublevels• The first energy level has only one type of orbital
(sublevel)– S
• The second energy level has 2 types of orbitals– S and P
• The third energy level has three types of orbitals– S, P and D
• The fourth energy level has four types of orbitals– S, P, D and F
• Successive energy levels follow the same pattern. • Relative energy: s < p < d < f
Principal Energy Level (n=?)
Orbital Types(sublevels available)
1 s
2
p
3
4
Orbital Shapess orbital: (one possible orientation)
2s
Orbital shapes• P orbital: ( three possible orientations)
Orbital shapes• d: orbital: ( five possible orientations)
Orbital shapes• f orbital: (seven possible orientations)
The Quantum Atom
Orbital Types(sublevels available)
# of orbital's per level
s 1
p 3
d 5
f 7
Principal Energy Level (n=?)
Total # of orbitals per P.E.L. (n2)
1 1
2
3
4
Orbital Types(sublevels available)
# of e’s per orbital type
s 2
p 6
d 10
f 14
Principal Energy Level (n=?)
Total # of e’s per P.E.L. (2n2)
1 2
2
3
4
Electron Configurations• Electrons fill the lowest energy levels first (H, Z=1)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s1
Lewis Dot Structures• Lewis dot structures are shorthand to represent the
valence electrons of an atom. • The structures are written as the element symbol
surrounded by dots that represent the valence electrons.
• Review Electron Configuration (H, Z=1)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s1
Lewis Dot Structures
Pauli Exclusion Principle• no two e- in an atom can have the same four
quantum numbers.
• each electron needs its own space.
• Result – an orbital can hold a maximum of 2 electrons with opposite spin
Fourth Quantum number is the Spin
Electron Configurations• Electrons fill the lowest energy levels first (He, Z=2)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s2
Electron Configurations• Electrons fill the lowest energy levels first (Li, Z=3)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s1
Electron Configurations• Electrons fill the lowest energy levels first (Be, Z=4)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s2
Electron ConfigurationsElectrons fill the lowest energy levels first (B, Z=5)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p1
Hund’s Rule• Don’t pair electrons in degenerate orbitals
until necessary.
• Unpaired electrons have the same spin.
• Applies to p, d, and f orbitals
2p
3d
Electron Configurations• Electrons fill the lowest energy levels first
(C, Z=6)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p2
Electron Configurations• Electrons fill the lowest energy levels first • (N, Z=7)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p3
Electron Configurations• Electrons fill the lowest energy levels first • (O, Z=8)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p4
Electron Configurations• Electrons fill the lowest energy levels first • (F, Z=9)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p5
Electron Configurations• Electrons fill the lowest energy levels first • (Ne, Z=10)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p6
Electron Configurations• Electrons fill the lowest energy levels first • (Na, Z=11)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p63s1
Lewis Dot Structures Chem Saver p 24• Lewis dot structures are shorthand to represent the
valence electrons of an atom. • The structures are written as the element symbol
surrounded by dots that represent the valence electrons.
Electron Configurations• Your Turn: Try Krypton (Kr, Z=36)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
Electron Configurations• Electrons fill the lowest energy levels first (Ca, Z=20)
5s
4s
3s
2s
1s
2p
3p
4p
3d
4d
E E N N E E R R G G YY
• 1s22s22p63s23p64s2
• An internet program about electron configurations is:
Electron Configurations
(Just click on the above link)
Diagonal Rule for Writing Configurations and Practice Chem Saver p 23
The relation between orbital filling and the periodic table
Chem Saver p 23ns1
np1
n-1d1
n-2f1
In your composition notebook complete, Z=11 to 54 odd only. Be sure to show the electron configuration short hand notation
and the Lewis dot structure for each.
1 s 2 s 2 p 3 s 3 p 4 s 3 d
4 p 5 s 4 d 5p
Electron Configuration on the Periodic Table
• The elements in the same family groups on the periodic table have similar physical and chemical properties
• The elements in the same family groups also tend to form similar types of compounds with other elements
• This is because the elements in the same family groups have the same number of electrons in the outer energy level
Short Hand noble gas configurations
