Warm Up
• Summarize the Bohr model of the atom in
your notes. Be sure to include information
about light and why elements emit colors
of light.
• Please turn in your flame test lab if you
have not already done so.
Quantum Mechanical Model:
The Modern View of the Atom
Flame Tests:
• When metal ion solutions are heated in
a flame different colors of light are
emitted.
• Each heated solution is giving off
different wavelengths of light
– This mixture of wavelengths can be broken
apart using a prism or spectroscope to
give the element’s emission spectrum
Light and Energy
• Each line corresponds to light with a
different energy.
– Red=Low Energy
– Blue (violet) = High Energy
• WHY are there only certain specific
amounts of energy given off???
Bohr Model of Atom:
• Model developed to explain H emission
spectrum
– Electron only allowed in specific circular
orbits
Orbits
Positive
Nucleus
electron
Low Energy
High Energy
Bohr Model and Energy
• Different orbits have different specific
amounts of energy (different energy
levels)
– Inner orbit has lowest energy (ground
state)
– As move away from nucleus orbits have
more energy
– If add a quantum of energy to electron it
moves to an orbit further out
Bohr continued…
• Electrons tend to fall to lower energy
– Give off a quantum of energy as a photon
– Different orbits are spaced closer or
further, therefore different quanta of
energy given off
• Observed as the lines with different colors
Bohr Model Energy Diagram
http://en.wikibooks.org/wiki/Astronomy/Molecular_Emission_and_Absorption
http://www.wiredchemist.com/images/hydrogen_electron.gif
Bohr Model Final Thoughts
• Explained emission of specific energies
(and wavelengths)
– Electron moved from an outer orbit to an
inner orbit
– Amount of energy given off = difference in
energy of the two orbits
• ONLY worked for Hydrogen (1 electron)
– Need a different model!
Heisenberg Uncertainty Principle
– It is impossible to precisely know both the
momentum and position of very small
particles at the same time.
– Only applies to very small particles (such
as electrons)
Quantum Mechanical Model of
the Atom
– Our current view of the atom
– Only certain allowed energies for electrons
• Energy Levels (kept from Bohr)
– No set paths which electrons follow
Quantum Mechanical Model of
the Atom
– Mathematical equation used to describe
the location of where the electron probably
is at any time
• Atomic orbital: Region of space where an
electron has a 90% probability of being located
– The probable location of the electron
dependant on the energy of the electron
Quantum Mechanical Model of
the Atom
- The electrons exist in Orbitals
– A region around the nucleus where an
electron with a given energy is likely to be
found
– They have characteristic shapes, sizes and
energies
– DO NOT describe how electrons actually
move
More Details of the Quantum
Mechanical Model
• Principal Quantum # (n)
– Describes principal energy levels of
electrons
– n = 1, 2, 3, 4, etc.
– Each principal energy level can be broken
into sublevels with slightly different amts
of energy
Details continued…
• Energy sublevels
– Each type of sublevel corresponds to a
differently shaped space in which the
electron is likely to be found
– Different sublevels have different #s of
orbitals
– Electrons in the orbitals of the same
sublevel have the same energy
Principal
Energy Level
Number of
Sublevels
Type of Sublevel
n= 1
1
1s (1 orbital)
n=2
2
n=3
3
n=4
4
2s (1 orbitals)
2p (3 orbitals)
3s (1 orbitals)
3p (3 orbitals)
3d (5 orbitals)
4s (1 orbitals)
4p (3 orbitals)
4d (5 orbitals)
4f (7 orbitals)
Orbital Shape and Orientation
• s sublevel
– 1 orbital: s
http://www.sparknotes.com/chemistry/fundamentals/atomicstructure/section1.html
Orbital Shape and Orientation
• p sublevel
– 3 orbitals: px, py, pz
– different orientations
andromeda.rutgers.edu/~huskey/335f07_lec.html
Orbital Shape and Orientation
• d sublevel
– 5 orbitals: dxy, dxz, dyz, dx2-y2, dz2
– different shapes and orientations
http://itl.chem.ufl.edu/2045_s00/lectures/lec_10.html
Orbital Shape and Orientation
• f sublevel
– 7 orbitals
– You DO NOT have to
know how to draw
these!!!
http://commons.wikimedia.org/wiki/File:F_orbitals.png
Energy Diagram
• shows relationship between each orbital
and amt of energy of electron in the orbital
http://www.chemistry.mcmaster.ca/esam/Chapter_4/section_3.html
Nature and Energy
• Nature goes toward the lowest energy
state
• Electrons in the atom tend to move
towards the most stable and lowest
energy arrangement
Warm Up
• Yesterday, we talked about the location of
the electrons in the atom. Describe the
shape and number of orbitals of each
sublevel discussed.
Orbital Diagram
• The arrangement of electrons in the
orbitals of the atom
How Electrons Fill Orbitals
• Electrons fill lowest
energy orbitals first
(Aufbau Principle)
How Electrons Fill Orbitals
• Each orbital can hold only 2 electrons
– Electrons in the same orbital have
opposite spins (Pauli Exclusion
Principle)
• Clockwise and counterclockwise
• On orbital filling diagram show one electron
as ↑ and the other as ↓
– Orbitals of the same energy will each
hold only 1 electron before any orbital
will hold a 2nd electron (Hund’s Rule)
Orbital Diagrams
– For H: _↑__
1s
Practice: He
Li
N
F
Exit Pass
• On a QUARTER piece of paper, write the
orbital diagram for Sulfur.
Electron Configuration
• Quicker format than the orbital diagram
• Write the energy level and letter for
each sublevel occupied by electrons
• Orbitals within the sublevel are
combined
– Use superscripts to show how many
electrons are in the sublevel
– Check by making sure superscripts add up
to the number of electrons in the atom
Electron Configuration Practice
• Oxygen
– 1s22s22p4
• Calcium
– 1s22s22p63s23p64s2
• Zinc
– 1s22s22p63s23p64s23d10
Use the Periodic Table for Electron
Configuration
– Structure of the PT tells us which orbitals fill when
doing electron configuration
http://genchem.chem.wisc.edu/sstutorial/Text5/Tx55/tx55.html
Electron Configuration
Practice
• Write the electron configuration for
each of the following:
–S
– Fe
– Br
–K
– Pb (CHALLENGE!)
Noble gas or Shortened Electron
Configuration
– A shorthand method to write electron
configurations
– For potassium: [Ar]4s1
– Practice:
• Calcium
• Phosphorous
Types of Electrons
• Valence electrons are in highest
principle energy level—Outer Electrons
– Elements in the same group have the same
# of valence electrons
• Explains similar chemical properties
• Core electrons are in lower principle
energy levels—Inner electrons