Transcript Chapter 6

CHEM 5013
Applied Chemical Principles
Chapter Six
Professor Bensley
Alfred State College
Chapter Objectives
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Describe waves in terms of frequency,
wavelength, and amplitude.
Interconvert between the frequency,
wavelength, and amplitude of light and
relate those quantities to characteristics
such as color and brightness.
Describe electromagnetic energy in terms
of the photon model.
Chapter Objectives
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Use Planck’s equation to calculate the
energy of a photon from its wavelength or
frequency.
Define the following terms: orbital, shell,
subshell, electron spin.
List and draw diagrams of the number of
orbitals of each type (1s, 3p, etc.) in an
atom.
Chapter Objectives
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Use the Pauli exclusion principle and
Hund’s rule to write electron
configurations for atoms and ions of main
group elements.
Explain the connection between valence
electron configurations and the periodic
table.
The Electromagnetic Spectrum
The Wave Nature of Light
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Light can be described by four variables.
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Wavelength, :
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Amplitude, A:
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Frequency, :
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Velocity, c:
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c = 
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Example
What is the wavelength of blue light with
a frequency of
6.4 x 1014 /s?
Check your answer – visible light is in the
range of 380 to 750 or so nm
The Wave Nature of Light
Refraction
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Notes:
Electromagnetic Spectrum
Quantum Effects and Photons
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What happens when you put metal in a
flame?
Atoms vibrate with a defined frequency
depending on the solid
Energy is added to atoms
Atom then loses energy and emits light.
Quantum Effects and Photons
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Photons:
E = h =
hc
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Absorption and Emission
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Step 1:
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Step 2:
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Step 3:
Atomic Spectra
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Atomic Spectra:
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Wavelengths are well separated or discrete.
Wavelengths vary from one element to the
next.
Atoms can only exist in a few states with very
specific energies.
When light is emitted, the atom goes from a
higher energy state to a lower energy state.
Atomic Spectra
 Example
The blue-green line of the
hydrogen atom spectrum has
a wavelength of 486 nm.
What is the energy in one
photon of this light?
Fundamental Concepts of the
Atom
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Electrons are
depicted as clouds
of negative charge
surrounding the
nucleus.
The
density of the
small dots is related to
the probability of
finding an electron at a
particular location.
Atomic Orbitals
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Think of them as addresses or locations:
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Streets (Shells)
Houses (Subshells)
Rooms (Orbitals)
Location of an electron is described by 4
quantum numbers.
Quantum Numbers
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Shells
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Subshells
Quantum Numbers
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Orbitals
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Electron Spin
Orbital Diagrams
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Orbital Diagrams:
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Electron spin represented by arrows (Spin Up, Spin Down)
Examples: Hydrogen, Helium, Lithium, Beryllium, Boron
Pauli Exclusion Principle
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No two electrons in an atom can have the same
four quantum numbers.
Which of the following electron configurations or
orbital diagrams are allowed and which are not
allowed by the Pauli Exclusion Principle? If it is
not allowed, explain why.
a) 1s22s12p3
b) 1s22s12p8
c) 1s22s22p63s23p63d8
d) 1s22s22p63s23p63d11
e)
1s
2s
Building Up Principle
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Ground State Electron Configuration:
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Excited State Electron Configuration:
Building Up Principle
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Chemical properties of an element are primarily
related to ground state electron configuration.
Example
H
Be
N
Ne
He
B
O
Na
Li
C
F
Do you see a pattern? This can be explained by
the building up principle (Aufbau Principle)
Building Up (Aufbau) Principle
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Obtain the electron
configuration by
successively filling
the subshells in this
order:
1s, 2s, 2p, 3s, 3p, 4s,
3d, 4p, 5s, 4d, 5p….
Building Up (Aufbau) Principle
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This order of subshells corresponds to increasing
energy levels of the subshells
We fill orbitals starting with lowest energy(1s)
and proceed to highest energy (building up)
H
Be
1s1
1s2 2s2
He
B
1s2
1s2 2s2 2p1
Li
1s2
2s1
Question?
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So what happens when you get to Carbon?
Hund’s Rule:
What is the electron configuration for the
ground state of sulfur?
Noble Gases
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Look at the Noble Gases (Ne, Ar, Kr, Xe) –
they are chemically inert. Why?
Shorthand electron configuration:
Core vs. Valence Electrons
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Two types of electrons represented in
shorthand electron configuration:
1.
Core electrons:
2.
Valence electrons:
Example
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Write the shorthand electronic configuration
for Sulfur.
So, how many valence electrons are there
in Sulfur?
The Periodic Table and
Electron Configurations
Periodicity of Elements
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Period # gives outermost shell containing electrons
in ground state.
Group number gives the number of valence
electrons.
Write the electron configuration for Tellerium.
(Atomic number = 52)
How many valence electrons in an atom of
Tellerium in the ground state?