Download LT1: Electron Arrangement (Ch. 5)

LT1: Electron Arrangement
(Ch. 5)
How do fireworks work?
Rutherford’s Model of the Atom
Contributions
Problems
• Nucleus: Explains where
positive protons and where the
mass of the atom is found
• Doesn’t explain electron
arrangement or
reactivity/properties of atoms
• Electron Arrangement:
electrons are outside the
nucleus flying in empty space
Characteristics of Waves
Electromagnetic Radiation
What is the relationship between
wavelength and frequency of EM
waves? How is Energy related?
What does amplitude tell you about
the wave?
Why did the wave model of light need
a revision?
It didn’t explain why metals
emit electrons when struck
by certain types of light.
It didn’t explain why only certain
colors are emitted from heated
objects.
Planck and Quantum
Matter can only gain a
CERTAIN AMOUNT OF
ENERGY= QUANTUM
The colors emitted from
an object when heated is
directly related to the
Quantum.
Is light a wave or a particle?
Why do we see colors from
signs?
neon
What do you think the
color depends on?
Why do some atoms emit green and
others emit red?
Explanation--- remember ROYGBIV
• Atoms are struck by Energy (light, flame,
electricity).
• The electrons are excited out of ground state to
excited state where they are unstable.
• As electrons fall back to ground state they give
off the energy they absorbed as LIGHT.
• The color depends on the quantum absorbed.
• Higher quantum= BIV
• Lower quantum= ROY
Atomic emission spectrum= set of
frequencies an atom gives offfingerprint for an atom
Bohr’s Model
Contributions
• ENERGY LEVELS:
• Electrons move in circular
patterns around the nucleus
like planets around the sun.
• Closer to the nucleus= lower
energy
• Further from nucleus= higher
energy
• QUANTUM NUMBER:
• n=1 closest to nucleus
• Movement from n= 2 to n=1
results in a photon
Visual
Problems with Bohr Model
• Doesn’t explain electron movement within
Energy Levels correctly
▫ Electrons DO NOT orbit like planets around the
sun
• Only works for Hydrogen
Accepted theory today: Quantum
Mechanical Model of the Atom
http://www.youtube.com/watch?v=-YYBCNQnYNM
• Electrons are treated like waves
• Electrons have certain ENERGY VALUES which dictate
their distance from the nucleus
▫ Lower energy ___________ the nucleus
▫ Higher energy __________ the nucleus
• DOES NOT explain electron path as “orbiting like
planets around the sun”
De Broglie and the Quantum
Mechanical Model
• Wave-like motion of electrons: all moving
particles have wave-like motion that restricts
how much energy the electrons can absorb and
emit (QUANTUM)
Schrodinger and the Quantum
Mechanical Model
• Atomic Orbitals: 3D space electrons are
likely to be found
▫ SHAPES electron fly in
Quantum Mechanical Model continued
• Principal Quantum Number (n)= #’s
assigned that correlates with:
▫
▫
▫
▫
Size
Speed of electron
Distance from the nucleus
Amount of energy electron has
• COLOR AND LABEL A PERIODIC TABLE
Atomic Orbitals
Quantum Mechanical Model cont.
• Principle Energy Level= correlates with the
distance from the nucleus and amount of energy
electron has.
• Energy sublevels= the number of orbitals in
each energy level
Type of
sublevel
Shape
# of orbitals (configurations)
Max # of
electrons
s
Sphere
1
2
p
Dumbbell
3
6
d
Clover
5
10
f
Complex
7
14
Can you fill in the rest by looking at a
Periodic table?
Energy
level or
Principal
Quantum
Number
1
2
3
4
5
6
7
Sublevels
Max #
of
electr
ons
1s
2s, 2p
3s, 3p, 3d
2
8
18
Heisenberg Uncertainty Principle
Electron ConfigurationMain Idea: A set of three rules can be used to determine
electron arrangement in an atom.
Aufbau
Electrons occupy lowest energy level first.
principle
Pauli
Exclusion
Principle
Electron have opposite spins if they are in the
same orbital.
Hund’s Rule
Electrons occupy each orbital before pairing.
Practice
• Electron configuration of Sodium:
• Orbital Notation of Sodium:
• Noble Gas Configuration of Sodium:
Exceptions to the Rules
• Many transition metals don’t follow the rules
• Copper and Chromium are common examples