Transcript Prelab notes

Electron Configuration
Radiant Energy
Waves
• Light travels as both
Waves and Packets of
energy.
• Light is a form of
Electromagnetic
Radiation.
– EM Radiation has
waves in the electric
and magnetic fields
• All waves (Water or
Electromagnetic) have
4 key characteristics:
–
–
–
–
Amplitude
Wavelength
Frequency
Speed
Wave Characteristics
• Amplitude.
– Height of a wave from
origin to a peak/crest.
– Affects brightness and
intensity.
• Wavelength.
– Distance from crest to crest.
Distance for one full cycle.
– Visible light: 400-750nm.
Wave Characteristics
• Frequency.
– How fast a wave oscillates
(moves up and down).
– Units: s-1, 1/s or Hz.
• Speed.
– Speed of light a constant:
3.00 X 108 m/s.
• Frequency and
Wavelength related by the
equation:  = c / 
Try this…
If the frequency of a wave is 93.1 x 106 s-1,
what is the wavelength?
Answer: 3.22 m
If the wavelength of a wave is 1.54 mm, what
is it’s frequency?
Answer: 1.95 x 1011 Hz (s-1)
Have a Problem?
Rearranging the equation:
• First, multiply by  (frequency):
   = (c/)  
• Now, divide by  (wavelength):
() /  = c / 
• Leaving:  = c/
Moving on….
Electromagnetic Spectrum
• Many parts including:
–
–
–
–
–
–
–
Gamma Rays (10-11 m)
X-Rays (10-9 m)
Ultra-violet (10-8 m)
Visible (10-7 m)
Infared (10-6 m)
Microwave (10-2 m)
TV/Radio (10-1 m)
Electromagnetic Spectrum
• Visible Spectrum:
ROY G BIV
– Red
– Orange
– Yellow
– Green
– Blue
– Indigo
– Violet
Electromagnetic Spectrum
(once more)
Electron Configuration
Quantum Theory
Early Puzzlements
• Wave model for light
was originally
accepted by scientific
community.
• This couldn’t explain
why metals heating
first emitted invisible
radiation and then
visible radiation.
• Other questions
included why elements
only emitted certain
characteristic colors of
light.
Plank’s Theory
• Every object can only
absorb or emit a
fundamental amount
of energy.
• This amount is called
a quantum.
• The amount is like
moving up or down
steps.
Plank’s Theory
• Plank’s Theory is
based on the
relationship between
frequency and the
energy of the particle.
• E = h
• Plank’s Constant:
– h = 6.6262 X 10-34 J-s
Quick Practice
If a wave has a frequency of 9.33x106 Hz,
what is it’s energy?
6.18x10-27 J
What is the frequency of a wave if its energy
is 4.32x10-31 J?
652 Hz
Photoelectric Effect
• Einstein used Plank’s equation to explain a
puzzling phenomenon, the Photoelectric Effect.
– Electrons ejected from metal when light shines on it.
– Metal need’s certain frequency of light to release
electrons. In Sodium, red light is no good, violet
releases them off easily.
– Photons: Tiny particles of light providing energy to
“knock off” electrons.
Dual Nature of Radiant Energy
• Proven in 1923 by
Arthur Compton
– Showed photon could
collide with an electron
like tiny balls.
• Summary:
– Light behaves as a
wave ( = c/)
– Light behaves as a
particle (E = h)
Electron Configuration
Another Look at the Atom
Line Spectra
• Def: A spectrum that
contains only certain
colors/wavelengths.
• AKA: The Atomic
Emission Spectrum
• Each element has it’s
own “fingerprint”
emission spectrum.
The Bohr Model
• Bohr drew the connection
between Rutherford's
model of the atom and
Planks idea of
quantization.
• Energy levels labeled with
Quantum Numbers (n)
• Ground state, or lowest
energy level – n=1
• Excited State – level of
higher energy
Matter Waves
• If energy has dual nature, why not matter?
• De Broglie thought so.
– Matter Waves – the wavelike behavior of waves.
– Didn’t stand without experimental proof
• Davison and Germer proved this with experiments
in 1927.
• Why don’t we see these matter waves? Mass must
be very small to observe wavelength.
Heisenberg Uncertainty
• Uncertainty Principle
– The position and momentum of a moving
object cannot simultaneously be measured and
known exactly.
• Translation:
– Cannot know exactly where and how fast an
electron is moving at the same time.
Electron Configurations
A New Approach to the Atom
Quantum-mechanics Model
• Includes all the ideas of the atom we have
covered:
– Energy of electrons is quantized
– Electrons exhibit wavelike behavior
– Electrons position and momentum cannot be
simultaneously known
– Model does describe the probable location of
electrons around the nucleus
Probability and Orbitals
• Electron Density:
– The density of an
electron cloud.
• Atomic Orbitals:
– A region around the
nucleus of an atom
where an electron with
a given energy is likely
to be found.
• Kinds of orbitals:
– Each kind has own
different basic shape.
– Given letter
designations of s, p, d
and f.
– s-orbitals are spherical
– p-orbitals are dumbbell
– d- and f-orbitals more
complex.
Orbitlas and Energy
• Principle energy levels
(n) can be divided into
sublevels.
• Number of sublevels
is equal to the number
of the principle energy
level.
Orbitals and Energy
• Each sublevel has one
or more orbitals
–
–
–
–
s – one
P – three
d – five
f – seven
• Summary provided in
figure 4-28 (pg 145)
Electron Spin
• Electrons have two spins:
– Up or clockwise
– Down or counterclockwise
• Only two electrons (one of each spin) can
occupy an orbital. These electrons are said
to be “paired”.
Electron Configurations
Electron Configurations