recap of last class
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Recap of Last Class. Recall: Werner Heisenberg formulated the Uncertanity Principle that states it is impossible for us to know an electron’s exact position (where it is) and momentum (where it is going) As a result, we cannot identify specific orbits that electrons travel in - PowerPoint PPT PresentationTRANSCRIPT
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Recall:◦ Werner Heisenberg formulated the Uncertanity Principle
that states it is impossible for us to know an electron’s exact position (where it is) and momentum (where it is going)
◦ As a result, we cannot identify specific orbits that electrons travel in
◦ We can only identify regions of space within an atom where an electron is most likely to be found ORBITALS!
◦ Schrodinger’s complex math equation allows us to: Calculate the shape of the electron cloud Probability of finding the electron at distinct locations within
those clouds
Recap of Last Class
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How do the Orbitals Fill Up with Electrons?
An Introduction to Electron Configurations
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Complete the activity “Welcome to Atomos Apartments!” on page 208
Assigning an Electron’s Address Explore
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We use electron configurations◦ The way electrons are arranged in atoms
There are rules to follow!◦ Aufbau principle
Electrons are added one at a time to the lowest energy orbitals available until all the electrons of the atom have been accounted for
“aufbau” German for ‘build up or construct’
Predicting Electron Locations
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aufbau chart
1s
3s
2s 2p
3d3p
4s 4p 4d 4f
5s 5p 5d 5f
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Pauli’s Exclusion Principle◦ An orbital can hold only two electrons
Predicting Electron Locations
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Hund’s Rule◦ “Electrons must fill a sub-level such that each
orbital has a spin up electron before they are paired with spin down electrons”
A bus analogy:◦ If you enter a bus and don’t know anyone on it, you will
pick a seat that is completely empty rather than one that already has a person in it
Predicting Electron Locations
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Electrons fill in order from lowest to highest energy The Pauli exclusion principle holds. An orbital can
hold only two electrons Two electrons in the same orbital must have opposite
signs (spins) You must know how many electrons can be held by
each orbital◦ 2 for s◦ 6 for p◦ 10 for d◦ 14 for f
Hund’s rule applies. The lowest energy configuration for an atom is the one having the maximum number of unpaired electrons for a set of orbitals◦ By convention, all unpaired electrons are represented as
having parallel spins with the spin “up”
Orbital Diagrams and Electron Configurations
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Just a thought…◦ How do you determine the number of electrons in
an element? Examples:
◦ Oxygen◦ Magnesium◦ Argon◦ Scandium
Electron Configuration Practice
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Orbital Notation
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Use the Noble Gas symbol to abbreviate or shorten the electron configuration◦ Krypton◦ Rubidium◦ Zirconium
Short-Hand Notation
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How Can We “Locate” an Electron?
Use Quantum Numbers!
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Each electron has a specific ‘address’ in the space around a nucleus
An electrons ‘address’ is given as a set of four quantum numbers
Each quantum number provides specific information on the electrons location
Quantum Numbers
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Electron Configuration
state
town
street
house number
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state (energy level) - quantum number n
town (sub-level) - quantum number l
street (orbital) - quantum number ml
house number (electron spin) - quantum number ms
Quantum Numbers
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Same as Bohr’s n Integral values: 1, 2, 3, …. Indicates probable distance from the
nucleus◦ Higher numbers = greater distance from nucleus◦ Greater distance = less tightly bound = higher
energy
Principal Quantum Number (n)
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Integral values from 0 to n - 1 for each principal quantum number n
Indicates the shape of the atomic orbitals
Table 7.1 Angular momentum quantum numbers and corresponding atomic orbital numbers
Angular Momentum Quantum Number (l)
Value of l 0 1 2 3 4
Letter used
s p d f g
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Integral values from l to -l, including zero Relates to the orientation of the orbital in
space relative to the other orbitals◦ 3-D orientation of each orbital
Magnetic Quantum Number (ml)
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Magnetic Quantum Number
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An orbital can hold only two electrons, and they must have opposite spins◦ Spin can have two values, +1/2 and -1/2
Pauli Exclusion Principle (Wolfgang Pauli)◦ "In a given atom no two electrons can have the
same set of four quantum numbers"
Electron Spin Quantum Number (ms)
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Complete the Closer on Page 206
Closer!
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Begin homework on page 209 – FRONT AND BACK!
Homework