Chapter 4 Electron Configurations
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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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Chapter 4 Electron Configurations. 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. What do you see?. What do you see?. - PowerPoint PPT Presentation
Transcript of Chapter 4 Electron Configurations
4-1 RADIANT ENERGY4-2 QUANTUM THEORY
4-3 ANOTHER LOOK AT THE ATOM4-4 A NEW APPROACH TO THE ATOM
4-5 ELECTRON CONFIGURATIONS
Chapter 4 Electron Configurations
What do you see?
What do you see?
• H AV IN G S E V ER A L D IF F E R EN T IM A G ES W / I N O N E I S A S C O N F U S I N G A S T H E M Y S T ERY O F EL EC T R O N S W ER E T O T H E S C IE N T I S T S.
• T H ER E WA S N O WAY T O S E E T H E M B U T T H EY K N EW T H E E L EC T R O N S MU S T B E T H E R E
• S C IE N T I S T S JU S T D ID N ’T K N O W W H AT T O D O A B O U T T H EM O R W H AT T H E Y S P E C I F I C A L LY D I D
WHAT ARE THE 4 CHARACTERISTICS OF AN ELECTROMAGNETIC WAVE? WHAT ARE
THE MAJOR REGIONS OF THE ELECTROMAGNETIC SPECTRUM?
4-1 Radiant Energy
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
Nature of Light
The properties of light: Properties of wave Properties of particles
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
Waves
All waves can be described by 4 characteristics Amplitude Wavelength Frequency speed
Amplitude
The height of the wave
Determines the brightness/intensity
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
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 HzRadio stations broadcast at megahertz
97.5 FM means the frequency of those radio waves are moving at 97.5 x 106 cycles per second
Visible light moves b/w 4 x 1014 – 7 x 1014 s-1
Speed of light
No matter the wavelength light moves at 3.00 x 108 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
λ = c/ν
λ : wavelengthc : speed of light – 3.00 x 108
ν : frequencyIf given the frequency of 4.74 x 1014 s-1, what
would the wavelength be?
Electromagnetic Spectrum
Types of waves: Infrared
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
???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?
Planck’s 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
Planck’s Theory
Quantum/quanta Fixed amount Goes against the previous theories of nrg
Planck’s Theory
E = hν E = energy h = 6.626 x 10-34 J-s
Unit: joule-second ν = frequency
Planck’s Theory
Using Planck’s theory, scientists can determine the temp of distant planets by measuring the λ of the electromagnetic radiation they emit
Planck’s Theory
Energies absorbed/emitted by atoms are quantized Means their values are restricted to certain quantities
What would happen if a car’s nrg was quantized? A car can only go so fast
Planck’s 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 can’t be occupied during this increase? No
How does a person’s 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.
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
Photoelectric Effect
Photons Particles of EM radiation No mass Carry a quantum of nrg nrg has certain minimum to cause ejection of
photoelectron Photon’s nrg must equal or exceed nrg needed to free an
e- from an atom nrg depends on frequency
Ephoton = hv
Photoelectric Effect
Photon strikes surface of metalPhoton transfers nrg to e- in metal atome- chooses to “swallow” whole photon
If swallowed, e- will use nrg to “jump” off the atomThe important, deciding factor is the ν of the
photon not the # of photonsSo why does violet light release e- but not
red? Violet has a greater ν, therefore a greater amount of
nrg/photon
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 ν which means high nrg photons wh.
could cause harm to living organisms Radio waves surround us w/o any warning signs
Low ν, low nrg photons wh. don‘t harm organisms.
READ THE “CHEMISTRY IN ACTION” BOX ON PAGE 132
Photoelectric Cells
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.
HTTP: / /WWW.YOUTUBE.COM/WATCH?V=_5F34NFWVL4
Recap Video
Group Activity
Each group will read their articleA PowerPoint will be made of the article
informationThe PowerPoint needs:
At least 5 slides At least 2 pictures/diagrams All members of the group presents
WHAT IS A LINE SPECTRUM? HOW DOES THE BOHR MODEL EXPLAIN THE LINE
SPECTRUM OF HYDROGEN?
4-3 Another Look at the Atom
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
Atomic Emission Spectra
The set of frequencies of EM waves emitted by atoms of a particular element
Explains neon signsEach element has a
unique spectrum and therefore can be identified within an unknown such as through a flame test Your lab last Monday
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
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 atom’s 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 Earth’s surfaceclimbing 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 atom’s 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 atom’s orbitals.
The Bohr Model of the Hydrogen Atom
Niels Bohr (1885-1962) Attended lecture of Rutherford and used his, Planck,
and Einstein’s theories Focused on Hydrogen
Simplest w/ only 1 e-
Using Rutherford’s “planetary orbit” model of e- around the nucleus, Bohr said that ea. “orbit” specified a certain quantum of nrg
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, etcExcited states represent larger orbits farther
from the nucleus
The Bohr Model of the Hydrogen Atom
The Bohr Model of the Hydrogen Atom
Physics 2000http://www.colorado.edu/physics/2000/quantumzo
ne/bohr.html
Matter Waves
Movement of e-
We draw the orbitals as circles but the e- don’t actually move in a circle around the nucleus
e- move around as waves Discovered by Louis de
Broglie 1924 Physicist French graduate
student
Heisenberg’s 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
Heisenberg’s 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
Heisenberg’s 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
Heisenberg’s Uncertainty Principle
States that there is no way to know exactly what an e- position and speed of an e- at any given time
Lasers
Read the Chemistry in Action on p 140
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 Heisenberg’s Uncertainty Principle?1. States the position and momentum of a moving object can’t simultaneously be
measured and known exactly4. 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.
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
Quantum Mechanical Model
Model of the atomExplains 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
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
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
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
Orbitals and Energy
Bohr suggested energies in electrons were quantized These quantizations labeled as principle quantum
levels designated by quantum #, nQuantum 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
Orbitals and Energy
Orbitals and Energy
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
Orbitals and Energy
Second energy level n = 2 2 sublevels
2s – slightly larger than 1s 2p – consists of 3 orbitals
(px, py, pz)• x, y, & z stand for axis (3D)
Orbitals and Energy
3rd principle energy level n = 3 3 sublevels
3s 3p 3d – five orbitals
Orbitals and Energy
4th principal energy level n = 4 4 sublevels
4s 4p 4d 4f – 7 orbitals
Electron Spin
Electrons spin either clockwise or counterclockwise
Each orbit has 2 electrons Each electron will have an opposite spin
Represented as arrows
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?
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
Aufbau Principle
All sublevels of an nrg level have equal nrg For example, in the 2p sublevel, the 2px, 2py, and 2pz
orbitals are all equal in sizeAn 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
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
Pauli Exclusion Principle
There are two e- in ea. orbitalea. 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.
Hund’s 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
Let’s look at some examples
Hund’s Rule
1. 2. 3.
4. 5. 6.
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-
Orbital Diagrams Cont.
Let’s 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- Let’s put them in our boxes, but put them in order of
orbitals
1s 2s 2p
Orbital Diagrams
With a partner, draw the orbital diagrams for Helium, Oxygen, and Fluorine
Electron Configuration Notation
Another way to represent the e- in an atomInstead of drawing boxes, you make a listFor our Carbon example, we had 6 e- total
1s22s22p2
We have a chart we can use to let us know which orbitals to place in our list first
e- configurations
With your partner, write the e- configurations of Helium, Oxygen, and Fluorine.
