Transcript Chapter 4 - Fredericksburg City Public Schools

Chapter 13
Electrons in Atoms
Quantum Mechanics
http://www.meta-synthesis.com/webbook/30_timeline/310px-Bohr-atom-PAR.svg.png
 Better than any previous model,
quantum mechanics does explain
how the atom behaves.
 Quantum mechanics treats electrons
not as particles, but more as waves
(like light waves) which can gain or
lose energy.
 But they can’t gain or lose just any
amount of energy. They gain or lose
a “quantum” of energy.
A quantum is just an amount of energy that the electron
needs to gain (or lose) to move to the next energy level.
In this case it is losing the energy and dropping a level.
What the heck is a Quantum?
http://www.blogcdn.com/www.slashfood.com/media/2008/08/splenda425.jpg
http://upload.wikimedia.org/wikipedia/commons/e/e9/Sucralose2.png
 Think of a quantum as a “packet” of
energy, much like a sugar packet at a
restaurant. A sugar packet contains a
teaspoonful of sugar.
 If the electron absorbs energy, it moves to
a higher energy level. If it emits (loses)
energy, it moves to a lower energy level.
 But like Bohr suggested in his model, the
electron has to gain or lose exactly the
right amount. That amount is a quantum
of energy.
 An electron can’t gain 1.5 or 2.4 packets. It
has to gain, or lose, a whole unit of
energy. Or two or three whole units.
C12H19O8Cl3 is the formula for sucralose, which is the chemical name for Splenda.
That “beast” molecule is sucralose. It’s an Organic compound.
Atomic Orbitals
http://milesmathis.com/bohr2.jpg
 Much like the Bohr model, the energy
levels in quantum mechanics describe
locations where you are likely to find
an electron.
 Remember that orbitals are
“geometric shapes” around the
An old Bohr??
nucleus where electrons are found.
Mwwhaha!
 Quantum mechanics calculates the
probabilities where you are “likely”
to find electrons.
Atomic Orbitals
http://courses.chem.psu.edu/chem210/quantum/quantum.html
 Of course, you could find an electron anywhere
if you looked hard enough.
 So scientists agreed to limit these calculations to
locations where there was at least a 90% chance
of finding an electron.
 Think of orbitals as sort of a "border” for
spaces around the nucleus inside which
electrons are allowed. No more than 2
electrons can ever be in 1 orbital. The orbital
just defines an “area” where you can find an
electron.
 What is the chance of finding an electron in
the nucleus? Yes, of course, it’s zero. There
aren’t any electrons in the nucleus.
Atomic Orbitals
http://www-hep.phys.unm.edu/~gold/phys492/orbitals.gif
3s
2s
1s
 Quantum mechanics doesn’t predict SPECIFIC orbits, like the Bohr model does.
 It allows you to describe orbitals. An orbital is “a region around the nucleus where 1
or 2 electrons will be located.”
 Some examples of those are shown above. The darkest shaded areas are most likely
to have electrons. The nucleus is at the exact center of each diagram.
Energy Levels
http://www.chem4kids.com/files/art/elem_pertable2.gif
 Quantum mechanics has a
principal quantum number. It is
represented by a little n. It
represents the “energy level”
similar to Bohr’s model.
Red
Orange
Yellow
Green
Blue
Indigo
Violet
n=1
n=2
n=3
n=4
n=5
n=6
n=7
 n=1 describes the first energy level
 n=2 describes the second energy
level
 Etc.
 Each energy level represents a
period or row on the periodic
table. It’s amazing how all this
stuff just “fits” together.
Sub-levels = Specific
Atomic Orbitals
 Each energy level has 1 or more
“sub-levels” which describe the
specific “atomic orbitals” for that
level.
Blue = s block
 n = 1 has 1 sub-level (the “s” orbital)
 n = 2 has 2 sub-levels (“s” and “p”)
 n = 3 has 3 sub-levels (“s”, “p” and
“d”)
 n = 4 has 4 sub-levels (“s”, “p”, “d”
and “f”)
 There are 4 types of atomic orbitals:
 s, p, d and f
 Each of these sub-levels represent the
blocks on the periodic table.
Orbitals
http://media-2.web.britannica.com/eb-media/54/3254-004-AEC1FB42.gif
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/D_orbitals.svg/744px-D_orbitals.svg.png
s
p
d

In the s block, electrons are going into s orbitals.

In the p block, the s orbitals are full. New electrons are going into the p orbitals.

In the d block, the s and p orbitals are full. New electrons are going into the d orbitals.

What about the f block?
Important
Constant Alert
h = 6.6 x 10-34 J
s
Objective B
https://reich-chemistry.wikispaces.com/file/view/Max_Planck_(1858-1947).jpg
 As we’ve already discussed, electrons
cannot have just any amount of energy.
 They have a certain amount of energy
which corresponds to a specific energy
level. We call that a quantum of energy.
 They can move to a different energy level,
by absorbing (or emitting) just enough
energy to move from one to the other.
Max Planck, another German Nobel Prize winner…
A German scientist who came up with the idea of the quantum. He not only
discovered it, but he figured out that the energy of the quantum was related to the
frequency of the light it absorbed or emitted.
E = h ×νwhere ν= frequency and h = Planck’s constant
Absorbing and Emitting Energy
http://farm3.static.flickr.com/2366/2475587698_44461ac193.jpg?v=0
http://wiki.answers.com/Q/What_gas_is_used_to_make_yellow-green_neon_signs
 You’ve seen this before. Neon atoms absorb and emit
energy. When they absorb a quantum of energy, they
go to an excited (higher energy) state.
 When they emit energy, and go back to the ground
(lowest energy) state, we can see that light as a red
color.
I’ll take a large dark
chocolate shake,
please.
 A neon sign is a glass tube which has neon gas in it.
The tube is connected to electricity which supplies
energy to the atoms. Not all “neon signs” have neon
in them though. See the little red box below. They
sometimes also put Hg or other elements in there to
give different colors.
“The noble gases fluoresce in different colors in gas discharge tubes. Helium is white to
orange, neon is red-orange, argon violet to pale lavender-blue, krypton white to greenish,
xenon whitish to blue green at high currents and radon is not specified.”
Objective C
 Let’s talk about atomic orbitals in a bit more
detail.
 Each principal energy level is described by a
principal quantum number. (That’s “n”).
 Each energy level can have one or more
sublevels (those describe the specific
geometric areas around the nucleus called
orbitals).
 Each orbital can hold a maximum of 2
electrons.
Objective C
Energy
Level
Sublevels
Total Orbitals
Total
Electrons
Total Electrons
per Level
n=1
s
1 (1s orbital)
2
2
n=2
s
p
1 (2s orbital)
3 (2p orbitals)
2
6
8
n=3
s
Complete
p
d
1 (3s orbital)
the3chart
in your
(3p orbitals)
5 (3d orbitals)
p
3 (4p orbitals)
f
7 (4f orbitals)

notes
2
as6 we
10
18
discuss this.
 The first level (n=1) has an s orbital. It has only 1.
orbitals in the first
n = 4 There
s are no other
1 (4s orbital)
2 energy level.
32
 We dcall this orbital
the 1s orbital.
5 (4d orbitals)
6
10
14
Where are these Orbitals?
http://www.biosulf.org/1/images/periodictable.png
1s
2s
2p
3s
3p
4s
3d
4p
5s
4d
5p
6s
5d
6p
7s
6d
7p
4f
5f
Shapes of These Orbitals
(the nucleus is ALWAYS at the center of the orbital)
 The s orbital looks like a ball or sphere.
 The p orbital looks like a dumb-bell.
 These orbitals are all perpendicular to each other.
 The d orbitals have two shapes.
 4 of the 5 look like “4-leaf clovers.”
 The 5th one looks like a “big dumb-bell” with a “hulahoop” around the middle.
 The shapes of the f orbitals are complex. They are
on the next slide, but you don’t need to remember
them, nor will they be on the test.
f orbitals
http://antoine.frostburg.edu/chem/senese/101/electrons/faq/f-orbital-shapes.shtml
g orbitals
http://jeries.rihani.com/index3.html
 Another hypothesis by Glenn Seaborg is that element number 121
will start “the g block.”
 The “g” block will be another grouping, similar to the
Lanthanides and Actinides, of 18 elements.
 I have a link on my website. Click on Seaborg’s Extended
Periodic Table and take a look. Maybe your grandchildren will
know for sure whether or not it turned out to be a correct
hypothesis.
 Since this is all science fiction, you obviously don’t have to know
what g orbitals look like.
 A collection of Dr. Seaborg’s most important scientific
publications has been published in a book called “Modern
Alchemist.”
The
th
8
Period…
 To date, no elements have been
discovered which have 8s electrons.
Element 119 is predicted to be the
first element in the “8th period.”
 Assuming it stays around long enough
to discover its properties, what do you
think some of its properties would be?
Let’s Summarize…
Type
Comment
s orbitals
Every level has 1 s orbital
p orbitals
Every level ≥ 2 has 3 p orbitals
d orbitals
Every level ≥ 3 has 5 d orbitals
f orbitals
Every level ≥ 4 has 7 f orbitals
“Science
Fiction”
Comment
g orbitals
It is thought that every level ≥ 5 will have g orbitals.
No elements have yet been discovered with “g”
orbitals. There would be 9 “g” orbitals per energy level.
Where does it
end?
Who knows? In the last 50 years, only about 14
elements have been “made” in the laboratory.
The 8th Period?
Element 119 will start the 8th period, if it is ever created.
Island of Stability
http://www.nytimes.com/1999/02/27/us/glenn-seaborg-leader-of-team-that-found-plutonium-dies-at-86.html
 This is another hypothesis from Dr. Seaborg. His thought was that
element 114 would be an “island of stability,” especially if it also had
184 neutrons.
 Most synthesized elements only last for fractions of seconds.
However, in 1998 researchers synthesized element 114 and it lasted
for 30 seconds. Perhaps this is the “shore” of the Island of Stability
that Dr. Seaborg hypothesized.
 The element 114 was made using some of the original Pu-244 that
Dr. Seaborg himself made in the early 1940s. They bombarded
plutonium with Ca-48 atoms to form some of the new element 114.
 To date, small amount of elements have been made up through Z =
118. Element 119 would be an element in the 8th period. This has
NOT been synthesized as of August, 2009, although I suspect
scientists around the world are currently working hard to do so.
Island of Stability
http://www.sciencecodex.com/files/Island%20of%20Stability%201.jpg
http://physicsworld.com/cws/article/print/19751
Famous picture of the “Island of Stability” showing the island off in the distance (top
right) with 114 protons and 184 neutrons. What would the atomic mass of the island
be? An element with Z = 184 is also predicted to be another “island of stability.”
However, we currently do not know how to make such a huge atom.
Electron Configurations
 What do I mean by “electron
configuration?”
 The electron configuration is the
specific way in which the atomic
orbitals are filled.
 Think of it as being similar to your
address. The electron configuration
tells me where all the electrons “live.”
Rules for Electon Configurations
https://teach.lanecc.edu/gaudias/scheme.gif
 In order to write an electron
configuration, we need to know the
RULES.
 3 rules govern electron
configurations.
 Aufbau Principle
 Pauli Exclusion Principle
 Hund’s Rule
 Using the orbital filling diagram at
the right will help you figure out
HOW to write them
 Start with the 1s orbital. Fill each
orbital completely and then go to the
next one, until all of the elements
have been acounted for.
Fill Lower Energy Orbitals
FIRST
Each line represents
an orbital.
1 (s), 3 (p), 5 (d), 7 (f)
High Energy
http://www.meta-synthesis.com/webbook/34_qn/qn3.jpg
 The Aufbau Principle states
that electrons enter the
lowest energy orbitals first.
 The lower the principal
quantum number (n) the
lower the energy.
Low Energy
 Within an energy level, s
orbitals are the lowest
energy, followed by p, d and
then f. F orbitals are the
highest energy for that level.
No more than 2 Electrons
in Any Orbital…ever.
http://www.fnal.gov/pub/inquiring/timeline/images/pauli.jpg
 The next rule is the Pauli Exclusion Principal.
 The Pauli Exclusion Principle states that an
atomic orbital may have up to 2 electrons and
then it is full.
 The spins have to be paired.
 We usually represent this with an up arrow and
a down arrow.
Wolfgang Pauli, yet
another German
Nobel Prize winner
 Since there is only 1 s orbital per energy level,
only 2 electrons fill that orbital.
Quantum numbers describe an electrons position, and no 2
electrons can have the exact same quantum numbers. Because of
that, electrons must have opposite spins from each other in order
to “share” the same orbital.
Hund’s Rule
http://intro.chem.okstate.edu/AP/2004Norman/Chapter7/Lec111000.html
 Hunds Rule states that when you
get to degenerate orbitals, you fill
them all half way first, and then
you start pairing up the electrons.
 What are degenerate orbitals?
 Degenerate means they have the
same energy.
 So, the 3 p orbitals on each level
are degenerate, because they all
have the same energy.
Don’t pair up the 2p electrons
until all 3 orbitals are half full.
 Similarly, the d and f orbitals are
degenerate too.
Objective D
 NOW that we know the rules, we can try to write
some electron configurations.
 Remember to use your orbital filling guide to
determine WHICH orbital comes next.
 Lets write some electron configurations for the first
few elements, and let’s start with hydrogen.
Objective D
 According to the orbital diagram, 1s is
the first orbital to be filled. Hydrogen
has one electron in that 1s orbital.
 The electron configuration for H is 1s1
 That means that Hydrogen has 1
electron (the superscript) and it is
located in the 1s orbital, which is the s
orbital in the 1st energy level.
 Every atom has only a single 1s orbital.
Cool
Orbital
Website
Objective D
http://library.thinkquest.org/10429/media/eleconfig/helium.gif
 Try to do Helium now.
 Helium has 2 electrons. Since each orbital can hold 2
electrons, He has 2 electrons in the 1s orbital, which means
that it is now full.
 What is the electron configuration for He? (yes of course it’s 1s )
2
Electron Configurations
Element
Configuration
Element
Configuration
H Z=1
1s1
He Z=2
1s2
Li Z=3
1s22s1
Be Z=4
1s22s2
B
Z=5
1s22s22p1
C
Z=6
1s22s22p2
N Z=7
1s22s22p3
O
Z=8
1s22s22p4
F
1s22s22p5
Ne Z=10
1s22s22p6
(2p is now full)
Na Z=11
1s22s22p63s1
Cl Z=17
1s22s22p63s23p5
K Z=19
1s22s22p63s23p64s1
Sc Z=21
1s22s22p63s23p64s23d1
Fe Z=26
1s22s22p63s23p64s23d6
Br Z=35
1s22s22p63s23p64s23d104p5
Z=9
Note that all the numbers in the electron configuration add up to the atomic
number for that element. Ex: for Ne (Z=10), 2+2+6 = 10
Objective D
 One last thing. Look at the previous slide and look
at just hydrogen, lithium, sodium and potassium.
 Notice their electron configurations. Do you see
any similarities?
 Since H and Li and Na and K are all in Group 1A,
they all have a similar ending. (s1)
Electron Configurations
Element
Configuration
H Z=1
1s1
Li Z=3
1s22s1
Na Z=11
1s22s22p63s1
K Z=19
1s22s22p63s23p64s1
This similar configuration causes them to behave the
same chemically.
It’s for that reason they are in the same family or group
on the periodic table.
Each group will have the same ending configuration, in
this case something that ends in s1.
Objective E
 The rest of this study guide deals with Section 3 of the
chapter.
 Electromagnetic radiation (EM radiation) is a continuous
spectrum of light which includes radio and TV waves,
gamma rays, infrared (heat), ultraviolet, and the tiny sliver
that we can see called visible light.
 There is a picture of the complete EM spectrum on pg 373
in your book.
 Visible light can be separated into colors by using a prism.
 The colors in the spectrum can be remembered with ROY
G BIV.
Objective E
http://www.optics.arizona.edu/Nofziger/UNVR195a/Day1/EMspectrum1.jpg
Objective E
 Light moves at a constant speed.
 The speed of light is 3.0 x 108 m/s. You need to remember
that number.
 We represent the speed of light with c. There is a formula
to calculate the speed of light, and it is
C=λxν
λ = wavelength and ν = frequency
Objective E
 C = λ x ν can be rearranged to solve for
wavelength or frequency
 λ=c/ν
 ν =c/λ
 Since c is a constant, the longer the
wavelength, the slower the frequency. The
shorter the wavelength, the longer the
frequency.
Objective E
http://www.windows.ucar.edu/physical_science/magnetism/images/visible_spectrum_waves_big.jpg
 The visible spectrum goes from red at
about 700 nm to violet at about 380 nm.
Objective E
http://i.ehow.com/images/GlobalPhoto/Articles/4750092/stove1-main_Full.jpg
 Just longer than red is
the “infrared” portion,
which is “heat waves.”
 That’s why a stove
burner glows red when
it’s very hot. Some of
the heat waves are very
close to the visible
portion and we see that
as red light.
Objective E
http://en.wikipedia.org/wiki/Sunscreen
http://crazy-jokes.com/pictures/sunscreen.jpg
 Just shorter than the
violet portion is the
ultraviolet radiation,
sometimes called UV
light. UV light is given
off by the sun and
causes you to tan and
burn. Tanning beds also
use UV lamps.
This pretty complicated formula is
how they mathematically calculate
SPF. Yes, you need Calculus to do
so. No, it won’t be on the test!!
where E(λ) is the solar irradiance spectrum,
A(λ) the erythemal action spectrum, and
MPF(λ) the monochromatic protection factor,
all functions of the wavelength λ.
Objective F
http://www.cbu.edu/~jvarrian/252/emspex.jpg
 Atomic emission spectrum is sometimes
called a line spectrum, to distinguish it
from the continuous spectrum.
Objective F
 Hydrogen has 4 lines in its atomic
emission spectrum (at least in the
visible portion that we can see).
 When hydrogen absorbs energy its
electrons go to an excited state and
then back, causing the lines in the
spectrum.
Objective F
 Only hydrogen gives off those 4
certain frequencies that it does.
 Other elements have different
spectra. Each element gives a
unique set of lines in its
spectrum.
Objective F
 Atomic emission spectra are therefore
“unique.” You can use the spectrum to
identify the element.
 It’s like a “fingerprint” which identifies the
light as coming from hydrogen, and not from
something else.
 Scientists can look at light from a distant star
and analyze it and determine what types of
elements make up that star.
 Just by looking at the light! Pretty impressive.
Objective F
 We can also relate energy of
the photon to frequency.
E=hxν
 h = Planck’s constant = 6.6 x
10-34
A photon is a
“particle” of
light.
Power Point Assignment
 Write electron configurations for the first 54
elements.
The End