Download Unit 3 - The Atom

*
How can we describe an atom?
How can atoms of the same element be both similar and different
at the same time?
What do we call an atom that is not neutral?
How can we calculate the average mass of isotopes?
How has the model of the atom evolved over time?
How can we describe the modern model of the atom?
How can we describe where are electrons are located within the
electron cloud?
How can we describe how electrons are arranged?
What is electromagnetic radiation?
How is light produced?
- Honors Chemistry
AIM: How can we describe an atom?
The Theory of the Atom
•
________________,
a famous Greek teacher who lived in the 4th
Democritus
Century B.C., first suggested the idea of the atom.
•
________
John __________
Dalton came up with his atomic theory based on
the results of his experiments.
The Atom
•
element
The smallest particle of an ________________
is an atom.
•
subatomic
The atom is made up of three ________________
particles.
1897 by J. J. Thomson by using
(1)The electron was discovered in _______
(−) charge. It’s mass
a cathode ray tube. The electron has a _______
is much smaller than the other 2 subatomic particles, therefore
ignored
it’s mass is usually ______________.
*Cathode Ray Tube
(+)
(2) The proton has a ______
charge, and it was discovered in
1886
_________
by E. Goldstein.
(3) The neutron does not have a charge. In other words, it is
neutral It was discovered in 1932
________.
____ by James Chadwick. The
mass as the proton.
neutron has about the same _________
visible matter
*These three particles make up all the ____________________
in the Universe!
*There are other particles such as neutrinos, positrons, and
quarks, but are typically left for 2nd year chemistry courses.
Nuclear Atomic Structure
*The atom is made up of 2 parts/sections:
(1) The ______________
--- (in the center of the atom)
nucleus
electron _________
cloud --- (surrounds the nucleus)
(2) The ____________
(p+ & n0)
e− cloud
The Nucleus
Rutherford in ________.
1911
*Discovered by Ernest ________________
*He shot a beam of positively charged “alpha particles”,
helium nuclei, at a thin sheet of ______
gold foil
which are ___________
_____.
• 99.9% of the particles went right on
detector
through to the ______________.
*
• Some were slightly deflected. Some
bounced
back
even ____________
________
towards the source!
• This would be like shooting a
cannon ball at a piece of tissue paper
and having it bounce off.
* Rutherford’s Experiment
* Conclusions about the Nucleus
(1) Most of the atom is more or less _________
empty ___________.
space
tiny
(2) The nucleus is very _________.
(Stadium Analogy)
dense
(3) The nucleus is very ___________.
(Large Mass ÷ Small Volume)
positively
(4) The nucleus is ______________
charged.
Counting Subatomic Particles in an Atom
protons
• The atomic # of an element equals the number of ____________
in the
nucleus.
protons
• The mass # of an element equals the sum of the _____________
and
neutrons
______________
in the nucleus.
electrons
• In a neutral atom, the # of protons = # of ______________.
subtract
• To calculate the # of neutrons in the nucleus, ______________
the
atomic # from the __________
mass
___________
#.
*
(1)
Practice Problems
Find the # of e-, p+ and n0 for sodium. (mass # = 23)
Atomic # = 11 = # e- = # p+
2)
# neutrons = 23-11 = 12
Find the # of e-, p+ and n0 for uranium. (mass # = 238)
Atomic # = 92 = # e- = # p+
# neutrons = 238-92 = 146
3) What is the atomic # and mass # for the following atom?
# e- = 15; # n0 = 16
Atomic # = 15 = # e- = # p+ Mass # = p+ + n0 = 15+16 =31
The element is phosphorus!
*
REMEMBER  P….E….N
Element Name
Symbol
Atomic # AMU
# of Protons # of
Electrons
K
19
# of
Neutrons
19
5
16
23
10
48
25
14
14
*AIM: How can atoms of the same
element be both similar and different
at the same time?- Isotopes
* Isotopes
*An isotope refers to atoms that have the same # of ___________,
protons
neutrons
but they have a different # of ___________.
mass #’s (or simply,
*Because of this, they have different _________
masses
different ___________.)
*Isotopes are the same element, but the atoms weigh a different
neutrons
amount because of the # of ______________.
Examples---> (1) Carbon-12 & Carbon-13
(2) Chlorine-35 & Chlorine-37
(The # shown after the name is the mass #.)
atomic
*For each example, the elements have identical ___________ #’s,
mass #’s, (# of n0).
(# of p+) but different _________
*Another way to write the isotopes in shorthand is as follows:
12
6
C
35
17
Cl
mass #, and the bottom # is the __________
atomic
The top number is the ________
subtracting
number. Calculating the # n0 can be found by _____________
the #’s!
* Figure 3.10:
Two isotopes of sodium.
* More Practice Problems
(1)
Find the # e-, p+ and n0 for Xe-131.
Atomic # = 54 = p+ = e−
2)
Find the # e-, p+ and n0 for
n0 = 131 − 54 = 77
63
29
Cu
Atomic # = 29 = p+ = e−
n0 = 63 − 29 = 34
3) Write a shorthand way to represent the following isotope:
# e- = 1
# n0 = 0
Atomic # = p+ = e− = 1
H-1 or
# p+ = 1
mass # = n0 + p+ = 1+ 0 = 1
1
1
H
*
Atomic Mass
12
*Based on the relative mass of Carbon-12 which is exactly _______.
*1 p+ ≈ __1 atomic mass unit (amu) 1 n0 ≈ __1 amu 1e- ≈ __0 amu
*The atomic masses listed in the Periodic Table are a “weighted
average” of all the isotopes of the element.
Weighted Average
Practice Problems:
(1) Mrs. Smith’s geometry semester grades are calculated using a
weighted average of three category scores:
Major Grades= 60% of your grade
Minor Grades= 30% of your grade
Semester Exam=10% of your grade
• If a student had the following scores, what would they receive for the
semester?
Major= 80 (B − )
Minor= 60 (D −)
Semester Exam=65 (D)
* Weighted Average
Step (1): Multiply each score by the % that it is weighted.
Step (2): Add these products up, and that is the weighted average!
60% x 80 = 48.0
30% x 60 = 18.0
+
10% x 65 = 6.5
72.5 (C−)
Add them up!!
A “normal average” would be calculated by simply adding the
raw scores together and dividing by 3…
80 + 60 + 65 = 205 ÷ 3 = 68.3 = D
* Average Atomic Mass
Practice Problems:
(2) In chemistry, chlorine has 2 isotopes:
Cl-35 (75.8% abundance) Cl-37 (24.23 % abundance)
What is the weighted average atomic mass of chlorine?
35 x 0.758 = 26.53
+
37 x 0.2423 = 8.9651
35.4951 amu
Add them up!!!
(3) Oxygen has 3 isotopes:
O-16 (99.76%) O-17 (0.037%)
Estimate oxygen’s average atomic mass.
Barely over 16.0 amu
O-18 (0.2%)
* Average Atomic Mass
(4) Copper has an average atomic mass of 63.546 amu. It contains
only two natural isotopes, which are Cu-63, with an isotope mass of
62.940 and Cu-65 with an isotope mass of 64.928. What are the
percent of the two isotopes in naturally occurring copper?
Avg. Atomic Mass = (%Cu-63 x Mass Cu-63) + (%Cu-65 x Mass Cu-65)
% Cu-63 + % Cu-65 = 100%
OR
% Cu-63 + % Cu-65 = 1
63.546 = (%Cu-63 x 62.940) + (%Cu-65 x 64.928)
*
1.
80%
2.
127I,
17% 126I, 3% 128I
50% 197 Au, 50% 198 Au
*
Nucleons: particles in the nucleus (protons and neutrons)
Nuclear Charge: charge of the nucleus (same at # of protons)
Examples:
1.
How many nucleons are there in an atom with an atomic number of 20
and 23 neutrons?
2.
What is the nuclear charge of an Iron atom?
*
*
* Ions
An atom can gain or lose electrons to become electrically charged.
+ charged atom created by ___________
losing e-’s.
Cation = (___)
*
*
*
Cations are ______________
than the original atom.
smaller
_____________
generally form cations.
Metals
Anion = (___)
e-’s.
− charged atom created by _____________
gaining
*
*
larger
Anions are ____________
than the original atom.
_______________
generally form anions.
Nonmetals
Practice Problems: Count the # of protons & electrons in each ion.
a) Mg+2
12
10
p+ = _____
e− = ______
b) F−1
9
10
p+ = _____
e− = ______
*
AIM: How has the model of the atom evolved over
time?- Modern Atomic Theory\
Atomic Models
(1)
•
•
•
Thomson
a ball of (+) charge containing a number of enucleus
no ________________
plum
pudding
often described as the “________ _______________”
atom.
Rutherford
(2)
•
•
Model:
Model:
nucleus
a ____________ of (+) charge surrounded by
a number of eneutrons
no _____________ and no e- orbitals
Atomic Models
Bohr
(3)
•
•
•
•
Model:
neutrons
a nucleus of (+) charge that also contains ______________
nucleus is encircled by e-’s located in definite orbits (or
paths).
fixed
e-’s have ___________
energies in these orbits
e-’s do not lose energy as they orbit the nucleus
Quantum Mechanical Model ( Wave Mechanical Model)
(4)
•
•
shape
no definite ____________
to the e- path (“fuzzy” cloud)
probability
orbits of e-’s based on the _________________
of finding the
e- in the particular orbital shape.
*
Bohr Atomic Model
http://www.slideshare.net/laburkett/history-of-the-atom
*
*Heisenberg showed that the more precisely the
momentum of a particle is known, the less
precisely is its position known:
h
(x) (mv) 
4
*In many cases, our uncertainty of the
whereabouts of an electron is greater than the
size of the atom itself!
*
*
Quantum
Mechanical
Model
AIM: How can we describe where electrons are
located? - Energy Levels
Diagram:
• The energy levels in an atom are
rungs of a ladder.
sort of like _________
• The more energy an electron has,
the __________
farther away from the
nucleus it usually will be.
• The energy levels are not evenly
spaced. They get ___________
closer
together as you travel farther away.
• To move from one “rung” to
quantum
another requires a “____________”
of energy.
*
continuous energy levels
quantized energy levels
* Quantum Numbers
location
*Describe the ______________
of the e-’s around the nucleus.
address
*Quantum #’s are sort of like a home _____________
for the
electron.
*This information about the location of the e-’s in an atom can
be used to:
properties for the
(1) determine chemical & physical _____________
elements.
Periodic
Table is organized.
(2) show how the _______________
__________
how and _____
why elements combine to form
(3) show _____
compounds.
* The Four Quantum Numbers
1.
Principal Q. #: Describes the _____________
distance
that the
electron is from the nucleus. The bigger the number, the
farther away the electron is.
___________
Example: (1=closest, 2, 3, 4...farther away)
principal
These distances are sometimes called _______________
energy
levels
______________
____________.
1
2
3
nucleus
2.
shape
Orbital Q. #: Describes the __________
of the electron’s path
around the nucleus with a letter: (s, p, d, & f) These are
sublevels
sometimes called “_____________”.
spherical cloud;
s=_____________
ellipsoid
p=_____________
or a 3-D figure 8;
*
*
d & f orbital shapes are
criss
complex ________crossing
_______________
ellipsoids, and some d’s
and f’s are an ellipsoid
with a doughnut or two
around the middle.
All of these orbital shapes
are based on the probability
of finding the electron in
the cloud.
f - orbitals
d - orbitals
*
s
p
d
s
p
f
d
s
p
s
*
1 sublevel
2 sublevels
3 sublevels
3. Magnetic Q. #: tells how many _________________
orientations
in 3-D there
are about the nucleus for each orbital shape.
s=___
1 orientation
3 orientations... (x,
p= ___
5 orientations
d= ___
7 orientations
f= ___
y, and z)
*The orientations are represented with a line or a box.
Examples: ___
distance of
1s
orbital is
spherical orbital at a
This means a __________
“__”
(close) to the nucleus. This
1
centered about the x, y, and z axis.
□□□
orbital with its
4
distance of “___”
4p
ellipsoid
This represents an ___________
____
3 possible orientations at a
from the nucleus.
*
4. Spin Q. #: describes how the electron in an orientation is spinning
up or
around the nucleus. This spin can be thought of as “____”
down
“________”.
(Some like to imagine it spinning “clockwise” and
arrow
“counterclockwise”.) The spin is represented as an ___________
in the direction of the spin.
spherical
_________
distance of
Example: ↑
This represents one electron in a
up
2s
orbital with spin “____”
at a
“___”from
the nucleus.
2
*Remember, the four quantum numbers tell us the location, or
“address” of each electron in an atom.
*This information is vital in understanding the layout of the Periodic
Table and the reasoning behind why and how atoms form bonds.
AIM: How can we describe how electrons are
arranged? - Electron Configurations
* Electron configurations are notations that represent the four
Quantum #’s for all of the electrons in a particular atom. Here are
the rules for these notations:
*Rule #1 (Aufbau Principle): Electrons fill ________
lowest energy
orbitals first.
Examples:
2s
1s would be filled before ____
3p
3s would fill before ____
Electron
Configurations
Silicon
↑ ↑
↑↓
↑↓ ↑↓ ↑↓
↑↓
(Energy Level Diagram)
↑↓
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
*Rule #2:
Only ___
2 electrons can fit into each orientation.
Example: ___
↑↓
1s
___
↑
2s
not ____
↑↓↑
1s
*Rule #3 (Pauli Exclusion Principle):
Electrons in the same
opposite
orientation have ______________
spin.
Example:
↑ ↓ not ___
↑↑
___
1s
1s
*Rule #4 (Hund’s Rule):
□
Monopoly
“_______________
rule”---> Every
“
” in an orbital shape gets an electron before any orientation
gets a second e-.
Example:
□□□
↑
↑
2p
↑
not
2p
□□□
↑↓
↑
*Rule #5:
*
The Exceptions
lower
Half-filled or completely filled d & f sublevels have ________
energies and are more stable than partially filled d’s and f’s.
*
This means that an atom can “borrow” one of its “s”
electrons from the previous orbital to become more stable.
Example:
↑↓
___
5s
becomes
↑ ↓ ___
↑↓
↑↓
↑↓
↑
___
___
___
___
4d
↑↓
___
↑
↑↓
↑↓
↑↓
↑↓
___
___
___
___
___
5s
4d
lower
* Because the 4d sublevel is now full, the atom is at a ________
more stable.
energy state and therefore _________
Electron Configurations
↑ ↑
↑↓
Silicon
↑↓ ↑↓ ↑↓
↑↓
(Energy Level Diagram)
↑↓
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
* Electron Configurations
Practice Problems:
Write the electron configuration notation for each of the following
atoms:
*Hydrogen
*Carbon
*Iron
*Bromine
Shorthand Method: Assumes we already know about the # of
*H
*C
*Fe
*Br
□.
* How Electron Configurations Relate to the
Organization of the Periodic Table
s
p
d
f
*
* Electron Configurations & Properties
*How do electron configurations relate to the chemical and physical
properties of an element?
same outer shell e- configurations have
*All elements with the _________
________
similar properties.
vertical
*This means that elements in the same ____________
group have
similar properties.
s
Examples: (1) Li, Na, K, Rb, and Cs all have __1lone “__”
e- for
their last orbital... (_____,
2s1 _____,
3s1 _____,
4s1 etc.) This makes all of
very
water to
them ___________
reactive. They all react with __________
produce hydrogen gas.
(2) Ne, Ar, Kr, Xe, and Rn all have the outer energy level
filled
2s2 2p6
3s2 3p6
completely __________
with electrons...(________,
________,
4s2 4p6 etc.) This makes all of them ______________.
inert
________,
They do not produce __________________!
compounds
More Practice Problems
Bromine
(1) Which element has its last electron as a 4p5? ___________
F, Cl, I, At
(2) Which elements are similar in properties as Bromine? __________
(3) What would the outer shell electron configuration look like for the
element underneath Radon, (Rn)?
…7s2 5f14 6d10 7p6
4f1
(4) Which electron is added after 6s2? ________
(5) Which element would “borrow” a 5s electron to get a half-filled
Mo
“d” sublevel? ___________
(6) What is the shape of the last orbital filled in Calcium, (Ca)? sphere
_____
(7) How many electrons are in the last “p-orbital” of Sulfur, (S)?
4
____
* Electromagnetic Radiation
*Any wave of energy traveling at a speed of ___________
light
is called
electromagnetic radiation.
*There are many types of electromagnetic radiation and
each type has
a different _______________
and _______________.
frequency
wavelength
*Here are the types of electromagnetic radiation from longest to
shortest wave or lowest to highest frequency. These are also in order
from lowest to highest energy.
* Electromagnetic Radiation
* AIM: What is Electromagnetic Radiation?
(1) Radio Waves -- used in __________________
communications
cook _______.
food
(2) Microwaves-- broadcasts TV signals and used to _____
heat _________
Snakes & ______
owls can
(3) Infrared (IR) -- we feel this as _____;
“see” this.
infrared image of a cat
infrared image of heating pipes under a floor
*
Infrared
Vision
* Electromagnetic Radiation
(4) Visible Light -- the only radiation we can detect with our eyes. It
prism
can be separated into the colors of the spectrum with a __________.
ROYGBIV
sunburn
Bees
(5) Ultraviolet (UV) -- gives you a _____________; _________ can
“see” this; some of this radiation from the sun gets blocked by the
ozone
___________ layer
flower photo under normal light
flower photo under UV light
* Electromagnetic Radiation
(6) X-rays -- used in medicine
Ouch!
* Electromagnetic Radiation
(7) Gamma Rays-- some radioactive substances give it off
Cosmic
*_______________Rays
– These are not part of the EM spectrum…
They are high energy particles (mostly protons); They cause the
northern lights.
Interesting superhero facts:
• Superman has x-ray vision.
• The Incredible Hulk was
“created” by an accidental
overdose of gamma radiation.
• The Fantastic Four were
“created” by cosmic rays.
* How Light is Produced
*When atoms get hit with
zapping
energy (by _____________
them with electricity or by
heating them up), the
____________
electrons absorb this energy
and __________
jump to a higher
energy level. Figure (a)
*As they immediately fall back
down to the “____________
ground
state”, they give off this
energy in the form of a particle
light (or other
of ___________
types of electromagnetic
radiation)photon
called a
_____________. Figure (b)
* How Light is Produced
*Each photon emitted has a
color
specific ___________
(or
frequency).
*The color of the light that is
given off depends on how
far the electron _______
fell
_____
(which depends on how big of
a jump it originally made.)
The farther the fall, the
greater energy the
___________
photon has.
*
* How Light is Produced
energy levels (or
*Since electrons are located only in certain __________
orbitals) around the nucleus, only certain specific _________
color of light
are emitted.
spectroscope
*Scientists use a _________________
to separate these colors into
bar code of color
bands of light. These bands of color look like a ______
which is characteristic of that element. No two elements produce the
spectrum
same ______________
of colors. This can be used to distinguish one
element from another contained in a sample. (See Fig. 13.11)
* Emission Spectrum
Hydrogen
Spectrum
Neon
Spectrum
*
Measuring the Energy of Photons
*The photons of light given off or absorbed by atoms have specific
energies that can be calculated according to the following formula:
E=hν
(E = h f…some textbooks write it this way.)
E = energy (in joules)
h = Planck’s constant = 6.63×10−34 J·s
ν (nu) = frequency of the light in units of Hertz (waves per second)…s-1
*The frequency of light can be determined if given the wavelength (in
meters) according to the following formula:
c=λν
(c = f λ…some textbooks write it this way.)
c = the speed of light = 3.0 x 108 m/s
λ (lambda) = wavelength (in meters)
Both of these equations are given to you on the AP Equation Sheet.
How hydrogen
produces the four
visible photons
All the Photons Produced by Hydrogen
*
* Louis de Broglie suggested that if light can have material
properties, matter should exhibit wave properties.
* He demonstrated that the relationship between mass and
wavelength was
* h = Planck’s constant and v = velocity
* Quantity mv is called its momentum
h
 = mv
*
http://www.brainpop.com/science/matterandchemistr
y/atomicmodel/