4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE ATOM 4-4 A NEW APPROACH TO THE ATOM...
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- 4-1 RADIANT ENERGY 4-2 QUANTUM THEORY 4-3 ANOTHER LOOK AT THE
ATOM 4-4 A NEW APPROACH TO THE ATOM 4-5 ELECTRON CONFIGURATIONS
Chapter 4 Electron Configurations
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- What do you see?
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- HAVING SEVERAL DIFFERENT IMAGES W/IN ONE IS AS CONFUSING AS THE
MYSTERY OF ELECTRONS WERE TO THE SCIENTISTS. THERE WAS NO WAY TO
SEE THEM BUT THEY KNEW THE ELECTRONS MUST BE THERE SCIENTISTS JUST
DIDNT KNOW WHAT TO DO ABOUT THEM OR WHAT THEY SPECIFICALLY DID
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- WHAT ARE THE 4 CHARACTERISTICS OF AN ELECTROMAGNETIC WAVE? WHAT
ARE THE MAJOR REGIONS OF THE ELECTROMAGNETIC SPECTRUM? 4-1 Radiant
Energy
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- Light Most of what we know about how e- behave in atoms was
learned from watching how light interacts w/ matter Light travels
through space and is a form of radiant nrg
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- Nature of Light The properties of light: Properties of wave
Properties of particles
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- Waves Light travels in waves like the ocean These waves are
electromagnetic wh. makes light a form of electromagnetic radiation
Electromagnetic radiation (x-rays, gamma rays, radio waves)
Electromagnetic waves have electric and magnetic fields oscillating
at right angles to each other and to the direction of the motion of
the wave
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- Waves All waves can be described by 4 characteristics Amplitude
Wavelength Frequency speed
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- Amplitude The height of the wave Determines the
brightness/intensity
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- Wavelength Distance b/w wave crests The distance it takes for
the wave to make 1 cycle Visible light has a wavelength b/w 400-750
nanometers
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- Frequency Tells how fast the wave oscillates up and down
Measures how many cycles a wave makes in 1 second Units: 1/s, s -1,
1 Hz Radio stations broadcast at megahertz 97.5 FM means the
frequency of those radio waves are moving at 97.5 x 10 6 cycles per
second Visible light moves b/w 4 x 10 14 7 x 10 14 s -1
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- Speed of light No matter the wavelength light moves at 3.00 x
10 8 m/s b/c the speed does not change, relationships b/w
wavelength and frequency can be made The shorter the distance b/w
the crests of a wave, the faster the wave oscillates up and down
The shorter the wavelength, the greater the frequency
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- = c/ : wavelength c : speed of light 3.00 x 10 8 : frequency If
given the frequency of 4.74 x 10 14 s -1, what would the wavelength
be?
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- Electromagnetic Spectrum
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- Types of waves: Infrared
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- Types of waves: x-rays
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- WHAT IS MEANT BY NRG QUANTIZATION? HOW IS THE NRG OF RADIATION
RELATED TO ITS WAVELENGTH? HOW DOES THE IDEA OF PHOTONS OF LIGHT
EXPLAIN THE PHOTOELECTRIC EFFECT? 4-2 Quantum Theory
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- ???Unanswered questions??? Why would metal radiate different
wavelengths at different temperatures? Start heating, no visible
light Starts to glow red White hot Why do different elements have
different colors?
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- Plancks Theory Max Planck (1858-1947) Proposed that there is a
fundamental restriction on the amounts of nrg that an object
emits/absorbs Called these pieces of nrg quantum
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- Plancks Theory Quantum/quanta Fixed amount Goes against the
previous theories of nrg
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- Plancks Theory E = h E = energy h = 6.626 x 10 -34 J-s Unit:
joule-second = frequency
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- Plancks Theory Using Plancks theory, scientists can determine
the temp of distant planets by measuring the of the electromagnetic
radiation they emit
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- Plancks Theory Energies absorbed/emitted by atoms are quantized
Means their values are restricted to certain quantities What would
happen if a cars nrg was quantized? A car can only go so fast
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- Plancks Theory Look at figure 4-11 on pg 132 In which direction
would a person walk on the ramp/stairs to increase her potential
nrg? Up the ramp/stairs Is there any location on the ramp that cant
be occupied during this increase? No How does a persons movement on
the stairs compare to a similar movement on the ramp? To climb the
stairs, a person can only occupy distinct levels/stairs Would the
motion of an elevator be continuous/not? Explain. Yes, the motion
is continuous, but people can only get off at certain levels.
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- Photoelectric Effect Albert Einstein (1879-1955) When light of
a certain frequency is shone on some metals, the electrons of that
metal will be emitted from the surface These emitted e- are filled
with nrg and can be used thereafter Solar calculators Camera light
meters Each metal has a minimum frequency of light to release e-
Example: sodium metal is not affected by red light no matter its
intensity. A very faint violet light however will cause the e- to
be emitted
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- Photoelectric Effect Photons Particles of EM radiation No mass
Carry a quantum of nrg nrg has certain minimum to cause ejection of
photoelectron Photons nrg must equal or exceed nrg needed to free
an e- from an atom nrg depends on frequency E photon = hv
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- Photoelectric Effect Photon strikes surface of metal Photon
transfers nrg to e- in metal atom e- chooses to swallow whole
photon If swallowed, e- will use nrg to jump off the atom The
important, deciding factor is the of the photon not the # of
photons So why does violet light release e- but not red? Violet has
a greater , therefore a greater amount of nrg/photon
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- Photoelectric Effect nrg of a photon explains effects of
different kinds of EM radiation Hospitals have signs warning that
x-rays are being used X-rays have high which means high nrg photons
wh. could cause harm to living organisms Radio waves surround us
w/o any warning signs Low , low nrg photons wh. dont harm
organisms.
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- READ THE CHEMISTRY IN ACTION BOX ON PAGE 132 Photoelectric
Cells
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- 4-2 Section Review p 134 (1-4) What does it mean to say that
nrg is quantized? The nrg emitted/absorbed by any object is
restricted to fixed amounts called quanta How is the nrg of a
quantum of radiant nrg related to its frequency? The higher the
frequency of light, the greater the nrg/photon Why do you not
ordinarily observe the quantization of nrg in the world around you?
Ea quantum of nrg is too small to notice in the everyday world
People who work around x-rays often wear film badges to monitor the
amount of radiation to which they are exposed. Why do x-rays expose
the film in the badge when other kinds of electromagnetic radiation
do not? X-rays have high frequencies. X-ray quanta have enough nrg
to expose the film, whereas lower frequency waves do not.
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- HTTP://WWW.YOUTUBE.COM/WATCH?V=_5F 34NFWVL4 Recap Video
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- Group Activity Each group will read their article A PowerPoint
will be made of the article information The PowerPoint needs: At
least 5 slides At least 2 pictures/diagrams All members of the
group presents
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- WHAT IS A LINE SPECTRUM? HOW DOES THE BOHR MODEL EXPLAIN THE
LINE SPECTRUM OF HYDROGEN? 4-3 Another Look at the Atom
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- Line Spectra A spectrum that only contains certain
colors/wavelengths Also called the atomic emission spectrum A
fingerprint of that particular element Ea. element has its own
color Sodium had a yellow color in your flame test
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- Atomic Emission Spectra The set of frequencies of EM waves
emitted by atoms of a particular element Explains neon signs Each
element has a unique spectrum and therefore can be identified
within an unknown such as through a flame test Your lab last
Monday
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- Atomic Emission Spectrum Not every color of the spectrum seen
in an emission spectrum b/c not all frequencies of light are
emitted Photo courtesy NASA Hydrogen spectrum Photo courtesy NASA
Helium spectrum
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- Why does it take more nrg for the painter to climb to the top
rung of the ladder? The electrons of an atom occupy orbitals around
the atoms nucleus that are similar to the rungs of a ladder. Why
does the paintbrush hit the ground with more energy when it falls
from the top rung? The painter is moving farther away from Earths
surface climbing to the top rung. The paintbrush had more potential
energy at the top of the ladder. Also, it takes energy for an
electron to move from an orbital close to the atoms nucleus to an
orbital farther from the nucleus, just as it takes energy to move
up the rungs of a ladder. For example, just as a person cannot step
between the rungs of a ladder, an electron cannot occupy the space
between the atoms orbitals.
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- The Bohr Model of the Hydrogen Atom Niels Bohr (1885-1962)
Attended lecture of Rutherford and used his, Planck, and Einsteins
theories Focused on Hydrogen Simplest w/ only 1 e - Using
Rutherfords planetary orbit model of e - around the nucleus, Bohr
said that ea. orbit specified a certain quantum of nrg
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- The Bohr Model of the Hydrogen Atom Bohr labeled ea. nrg level
(orbit) w/ a quantum #, n The lowest nrg level (closest to
nucleus), called ground state n = 1 When the e- absorbs the right
amount, it jumps to a higher nrg level Called an excited state
Quantum #s: n=2, n=3, n=4, etc Excited states represent larger
orbits farther from the nucleus
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- The Bohr Model of the Hydrogen Atom
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- Physics 2000 http://www.colorado.edu/physics/2000/quantumzone/
bohr.html http://www.colorado.edu/physics/2000/quantumzone/
bohr.html
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- Matter Waves Movement of e - We draw the orbitals as circles
but the e- dont actually move in a circle around the nucleus e-
move around as waves Discovered by Louis de Broglie 1924 Physicist
French graduate student
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- Heisenbergs Uncertainty Principle If I put a balloon into a
completely dark room, could you locate it without moving the
balloon? It is nearly impossible Every time you touch the balloon
it moves! The e- is just like this
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- Heisenbergs Uncertainty Principle Cont. What if we put that
same balloon in the dark room and gave you a flash light? Would you
be able to find it now? Yes, the tiny photons from the light
reflect off the balloon & back into your eyes so that you see
the balloon w/o having to touch it
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- Heisenbergs Uncertainty Principle Cont. When you hit the
balloon w/ the photons, the balloon is so much bigger than the
photons When you hit an e- with a photon, the photon is the same
size as the e- so they reflect off one another After the collision
the e- is now going in a different direction and is usually going
much faster than before
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- Heisenbergs Uncertainty Principle States that there is no way
to know exactly what an e- position and speed of an e- at any given
time
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- Lasers Read the Chemistry in Action on p 140
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- 4-3 Section Review 1. What is the difference b/w a line
spectrum and a continuous spectrum? 1. Line spectrum contains only
certain colors/wavelengths. Continuous spectrum contains all
colors, wh. Fade gradually into ea. other 2. How does the Bohr
model account for the line spectrum of the hydrogen atom? 1. The
Bohr model labels the different nrg levels wh. Can be occupied by
an e-. The e- absorbs/emits a certain quantity of nrg when it moves
b/w these nrg levels. The frequencies in the line spectrum of
hydrogen correspond to the quantity of nrg emitted when an e- moves
from a higher to lower state. 3. What is Heisenbergs Uncertainty
Principle? 1. States the position and momentum of a moving object
cant simultaneously be measured and known exactly 4. You have
learned that in attempting to locate an e-. The act of measurement
changes the system. Suppose that you measure the temp. of a cup of
hot tea with a cold thermometer. How does the use of the cold
thermometer affect the temp reading? Is this an example of the
uncertainty principle? Explain.
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- WHAT IS AN ATOMIC ORBITAL? HOW DO THE S, P, D, AND F ORBITALS
COMPARE IN SIZE, SHAPE, AND ENERGY? 4-4 A New Approach to the
Atom
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- Quantum Mechanical Model Model of the atom Explains properties
of the atom by treating electrons as waves that have quantized
their energies Though unable to tell exactly where an electron is
or how it is moving Model does describe probability that electrons
will be found in certain locations around the nucleus
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- Probability and Orbitals Electrons are seen in a blurry cloud
or negative charge electron cloud More dense the area, the more
probable to find electrons Electron density: density of an electron
cloud High probability high electron density Low probability low
electron density
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- Probability and Orbitals The probability of finding electrons
in certain regions of an atom is described by orbitals An atomic
orbital is a region around the nucleus of an atom where an electron
with a given energy is likely to be found Orbitals have
characteristic shapes, sizes, and energies
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- Probability and Orbitals 4 kinds of orbitals s, p, d, and f s
orbital Circle shaped Increase in size w/ ea. increase in nrg level
p orbital Dumbbell/figure eight shaped d orbital No definite shape
f orbital No definite shape
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- Orbitals and Energy Bohr suggested energies in electrons were
quantized These quantizations labeled as principle quantum levels
designated by quantum #, n Quantum Mechanical Model adds sublevels
to these principle quantum levels Sublevels have a pattern # of
sublevels equals the quantum # n = 1 1 sublevel n = 2 2 sublevels,
etc
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- Orbitals and Energy
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- Just like an address You have a name, street, city, state, and
zipcode An electron has its principal energy level, the sublevel,
and its orbital within that sublevel First energy level n = 1 One
sublevel s Called the 1s sublevel and 1s orbital
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- Orbitals and Energy Second energy level n = 2 2 sublevels 2s
slightly larger than 1s 2p consists of 3 orbitals (p x, p y, p z )
x, y, & z stand for axis (3D)
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- Orbitals and Energy 3 rd principle energy level n = 3 3
sublevels 3s 3p 3d five orbitals
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- Orbitals and Energy 4 th principal energy level n = 4 4
sublevels 4s 4p 4d 4f 7 orbitals
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- Electron Spin Electrons spin either clockwise or
counterclockwise Each orbit has 2 electrons Each electron will have
an opposite spin Represented as arrows
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- 4-4 Review (p 146 1-4) What is an atomic orbital? An electron
orbit? Sketch the general shape of an s orbital and of a p orbital.
List the kinds of sublevels in the fourth principal energy level of
an atom. How many electron can be found in any orbital of an atom?
Are their spins parallel or opposite?
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- Ground-State e- Configuration Atoms want all their e- in a
pattern and where they are supposed to be (organized) When an atom
has a lot of e-, they want them in the lowest nrg levels as
possible
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- Aufbau Principle All sublevels of an nrg level have equal nrg
For example, in the 2p sublevel, the 2p x, 2p y, and 2p z orbitals
are all equal in size An f sublevel has more nrg than a d orbital,
wh. has more nrg than a p, wh. has more nrg than an s For example,
a 2p is larger than a 2s
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- Aufbau Cont It is possible for sublevels in one nrg level to
overlap sublevels in another nrg level For example, looking at nrg,
a 4s orbital would be smaller than a 3d orbital We would normally
think they would go in order
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- Pauli Exclusion Principle There are two e- in ea. orbital ea.
one has a different spin to it. A 2s orbital would have 2 e- in it
A 2p orbital would have 2 e- in ea. of its orbitals (x, y, and z)
These different spins, mean one is spinning clockwise and the other
counterclockwise.
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- Hunds Rule For ea. orbital in a sublevel (s, p, d, or f) will
need special placement of the e- There are 2 e- in ea. orbital, for
however many orbital you have w/in a sublevel (1 for s, 3 for p,
etc), you will need to place e- with the same spin in first and
then add the others Lets look at some examples
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- Hunds Rule 1. 2.3. 4.5.6.
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- Orbital Diagrams A way to represent the e- in an atom Lets you
see the different spins in an orbital What does it look like? Empty
box empty orbital Single up arrow orbital w/ 1 e- Up and down arrow
orbital w/ 2 e-
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- Orbital Diagrams Cont. Lets look at Carbon When we look at the
periodic table, Carbon has an atomic # of 6 we know that means
there are also 6 e- Lets put them in our boxes, but put them in
order of orbitals 1s2s2p
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- Orbital Diagrams With a partner, draw the orbital diagrams for
Helium, Oxygen, and Fluorine
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- Electron Configuration Notation Another way to represent the e-
in an atom Instead of drawing boxes, you make a list For our Carbon
example, we had 6 e- total 1s 2 2s 2 2p 2 We have a chart we can
use to let us know which orbitals to place in our list
firstchart
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- e- configurations With your partner, write the e-
configurations of Helium, Oxygen, and Fluorine.