Transcript Unit 2 Notes unit_2_atomic-nuclear-electronic

Unit 2 Atomic/Nuclear
Theory/Periodic Patterns
Unit Sequence
Day
Objectives
Assessments
Activities & Assignments
1
Hook Interest
Data & Observations,
Gold penny taped in
notebook, 1 page story
Alchemist’s Dream Lab,
Write 1 page story of
fictional discovery &
consequences
2
Overview of Atomic
Theory
Fireworks Poster Project
Rubric
History, Chemistry,
Spectra of Fireworks
2
Review basic Atomic
Structure
Previous knowledge in
notes, Completed
assignment, Cooperative
Quiz
Use atomic mass &
number to draw Bohr
Models of elements 1-18
odd
Quiz
3,4,5,6
History of Atomic
Theory – Dalton,
Thomson, Rutherford,
(Emission Spectra &
Photoelectric effect)
Bohr
Lecture discussions, pair
questions, Dalton Quiz –
Informal, Thomson Quiz,
Rutherford quiz,
Comparative Quiz
Lectures, Cathode Ray
Demos, Video Clips,
Flame Tests Lab,
Emission Spectra
Unit Sequence
Day
Objectives
Assessments
Activities & Assignments
7
Isotopes, Avg
Atomic Mass, Ions
810
RadioactivityDesigning
Experiments
Lab check points, Graphical
sharing on doc viewerk,
data & observations in NB
Radioactivity Shielding Lab
– Practice Day 1, Collect
Good Data Day 2, HW:
Graph, Share Data Day 3
½ Lives
Graphical Results
½ Life Quiz
½ Lives Blocks
½ Life Problems
11
Types of
Radioactivity
Informal Quiz
Notes & Geiger Counter
Demos
Book Questions about
basics & applications
12
Nuclear Equations
Discuss, Review & Quiz
Styrofoam balls demo, Write
equations for Uranium
decay series
Book questions, Worksheet
– Problem Solving to be
developed / Quiz
Unit Sequence
Day
Objectives
Assessments
Activities & Assignments
13
Understand
Quantum
Mechanics
Quiz Partner
Book questions, Demo
Standing Waves, Video –
Orbitals, Slides, Orbitals.
14
Electron
Configurations
Discuss as show config vs
diagram from H  Na,
Write configurations 1-35
odd
15
Periodic Patterns of
Electron
Configurations -
Quiz – configs, Noble Gas
configurations & drawing
Discovery discussion &
decorate patterns of
periodic table, write Noble
Gas configurations of 1-35
odd
16
History of Periodic
Table
Progress on mystery,
discussion feedback, quiz
partner
Cochran – Periodic Table
Mystery, Book questions,
Notes on History
17
Patterns of
Periodicity
-Reactivity,
bonding, ions,
atomic radius,
ionization energy,
electronegativity
Comparing Periodic Groups
Laserdisc demos of
radioactivity, decorate
bonds & ions on blank, use
data to make graphs &
interpret patterns
Element Samp;e
Observations
Unit Sequence
Day
Objectives
Assessments
Activities & Assignments
13
Understand
Patterns of Atomic
Radius & their Basis
Rank atoms vertically &
horizontally – small to large.
Explain trend of each.
Find patterns in pictures of
radii. Examine Explanation
14
Understand how
Periodic Table is
organized
15
16
17
Periodic Card Set
Old Periodic Table Fill in
Blank
Vocab 2A
• Atom
• Law of Definite
•
•
•
•
•
•
•
•
•
•
•
•
Proportions
Law of Conservation of
Mass
Cathode ray
Cathode ray tube
Electron
Nucleus
Proton
Neutron
Atomic mass unit
Atomic number
Atomic mass
Ion
Isotope
•
•
•
•
•
•
•
•
•
•
•
•
•
Electromagnetic radiation
frequency
Wavelength
Quantum
Photoelectric effect
Photon
Line spectrum
Ground state
Excited state
Quantum mechanical
model
Orbital
Sublevel
Electron configuration
Vocabulary 2B
Isotope
nuclear reactor
Radioisotope
nuclear weapon
Radioactivity
half life
Radiation
nuclear equation
Fission
positron
Fusion
radiocarbon dating
Radioactive decay
critical mass
Alpha particle
nuclear bombardment
Beta particle
strong nuclear force
Gamma ray
plasma
Nuclear chain reaction
dosimeter
Atom Builder Activity
• http://www.pbs.org/wgbh/aso/tryit/atom/
• For each addition to the atom (Up to
Stable Carbon) record the following:
Element
Protons
Neutrons
Electrons
Radioacti Ionized?
ve?
Stable?
Bohr Models of Atoms – Parts (1 of 3)
Part
Charge
Mass
Location
Proton
+1
1 amu
Nucleus
Electron
-1
1/1837
amu
Orbiting
nucleus
Neutron
0
1 amu
Nucleus
Determining the Part (2 of 3)
Part
How to Determine
Protons
= atomic number (smaller whole
#) from periodic table
Electrons
= atomic number (smaller whole
#) from periodic table (assumes
0 charge, or neutral)
Neutrons
= atomic mass (larger # w/
decimal, round) – atomic #
Drawing Bohr Models (3 of 3)
Determine number of protons, electrons &
neutrons in atom.
Draw protons (+) & neutrons (0) in nucleus.
Draw electrons in circles around nucleus:
- 2 maximum on 1st level.
- 8 maximum on 2nd level.
- 18 maximum on 3rd level.
Asmt: Draw elements 1-18 odd (even XC)
Alchemist’s Dream Review (1 of 2)
Q: How do you tell if it is really gold?
• Archimedes Principle: Determine the volume by
displacement and then confirm the density.
Q: What did the salty vinegar do?
• Dark pennies have black CuO oxidation.
• Acid in vinegar & salt reduce the Cu+2 back to Cu0 to
reshine the penny.
Q: How did the pennies turn silver?
• Zinc plates on the outside of the copper.
Q: How did they turn to gold in the flame?
• Heating melts the zinc into the copper to form brass!
Alchemist’s Dream Review (2 of 2)
Q: Was the removal of black CuO a chemical or physical
change?
A: It chemically changed from black copper salt to
metallic copper.
Q: Is brass a mixture or a compound?
A: Brass is a mixture and an alloy.
Q: Is the mixture homogeneous or heterogeneous?
A: Ours varied by depth and color. So they were
heterogeneous. Manufacturers produce homogeneous
brass.
Development of Atomic
Theory
History of the atom
• Not the history of atom, but the idea of the
atom.
• Original idea Ancient Greece (400 B.C.)
• Democritus and Leucippus- Greek
philosophers.
John Dalton
• British
• A small town
school teacher at
the age of 12.
• Introduced his
atomic theory in
1803.
Previous Findings
1. Law of Conservation of Mass
Matter is neither created or destroyed in a
chemical reaction. (Antoine Lavoisier)
2. Law of Definite Proportions
The percentage by mass of elements in a
compound is constant for any sample. Ex: H2O
3. Law of Multiple Proportions
Compounds composed of the same two
elements differ in one element by simple ratios.
Ex: CO vs CO2; H2O vs H2O2
Law of Definite Proportions
• Each compound has a
specific ratio of elements.
• It is a ratio by mass.
• Water has a mass of 18 grams
hydrogen 2 atoms x 1.0 grams
oxygen 1 atom x 16 grams
• The ratio is always 8 grams of oxygen
for each gram of hydrogen
(2 g H to 16 g O or 1 g H to 8 g O).
Law of Multiple Proportions
• Two elements or more elements may form
more than one compound if they have
different whole number ratio of each
element.
• Example: water
H2O
hydrogen peroxide
H2O2
Daltons Atomic Theory
1. All matter is composed of tiny indivisible
particles called atoms
2. All atoms of the same element are identical
3. Different elements have different types of
atoms
4. Compounds are formed from simple
combinations of atoms of different elements.
5. In a chemical reaction atoms are simply
rearranged.
*Activity: Ball & Stick Reactions
Picture Dalton’s Atomic Theory
Updates to Dalton’s Theory
1a. Atoms are divisible into protons,
neutrons & electrons (& even smaller!).
1b. In nuclear decay they actually fall
apart!
2. All atoms of a single element have the
same number of protons, but not
neutrons. (isotopes)
4. Compounds may be very complex!
Dalton’s Atomic Theory Quiz
1. What year was his theory published?
2. Which previous finding defined
compounds as having consistent percent
compositions?
3. How did Dalton describe chemical
reactions?
4. How can atoms of the same element be
different?
Cathode Rays
• Tape Lab – Static
•
•
•
electricity attractions &
repulsions. Where do the
charges originate?
An evacuated glass tube
when placed in an electric
field
Crooke’s observed a
glowing inside.
Thomson repeated
Crooke’s experiment and
did additional
experiments.
(-)
(+)
Thomson’s Experiment #1
• Setup: A cross was
•
•
placed in the path of
the glowing beam.
(D?)
Observation: A
shadow appeared on
the anode (+) side.
(D?)
Interpretation: The
rays come from the
cathode (-) side.
Cathode (-)
Anode (+)
Thomson’s Experiment
Voltage source
-
+
Vacuum tube
Metal Disks
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source

+
Passing an electric current makes a beam
appear to move from the negative to the
positive end
Thomson’s Experiment
Voltage source

+
Passing an electric current makes a beam
appear to move from the negative to the
positive end
Thomson’s Experiment
Voltage source

+
Passing an electric current makes a beam
appear to move from the negative to the
positive end
Thomson’s Experiment
Voltage source

+
Passing an electric current makes a beam
appear to move from the negative to the
positive end
Thomson’s Experiment #2
• Setup: The cathode
•
•
ray tube was placed in
an electric field: (-)
electrode on top, (+)
electrode on bottom.
(DPath?)
Observation: The
cathode rays were
attracted towards the
(+) electrode. (D?)
Interpretation:
Cathode rays must be
negative (-).
Thomson’s Experiment #3
• Setup: Cathode rays
•
•
were placed in a
magnetic field.
Observation:
Cathode rays are bent
perpendicular to the
magnetic field.
Interpretation:
Cathode rays are not
a form of light.
Thomson’s Experiment #4
• Setup: A glass wheel was placed on a
level track inside the cathode ray tube.
• Observation: Cathode rays can rotate the
glass wheel.
• Interpretation: Cathode rays are particles
with mass.
Thomson Experiment #5
• Setup: Thomson made cathode ray tubes
with a variety of different gases & metal
electrodes in the tube.
• Observation: Every tube produced the
same cathode rays.
• Interpretation: Cathode rays are
fundamental to matter. He called cathode
rays “electrons!” Discovered in 1897.
Thomson’s Plum Pudding Model
• Thomson concluded
•
that all atoms must
have negative
charges and positive
charges to balance
them.
Thomson assumed
that (+) & (-) charges
would be evenly
distributed.
Thomson’s Atomic Model
Thomson believed that the electrons were like plums
embedded in a positively charged “pudding,” thus it
was called the “plum pudding” model.
Uses of cathode rays
• 1. A cathode ray tube (CRT) is widely used in research laboratories
to convert any signal (electrical, sound, etc) into visual signals.
These are called CRT or oscilloscopes.
• 2. CRT is the basic component in all television and computer
screens. The signals are sent to the vertical and horizontal
deflecting plates, which produce a pattern on the fluorescent
screen.
• High energy cathode rays when stopped suddenly produce X-rays.
The X-rays have many medical and research applications.
Thomson’s Atomic Theory Quiz
1. How did Thomson know that the rays
came from the cathode?
2. What did Thomson conclude from
cathode rays being bent by a magnet?
3. How did Thomson know cathode rays
were fundamental to matter?
4. In Thomson’s model of the atom where
is the positive charge?
Millikan’s Oil Drop Experiment
• the charge of an
electron with this
oil-drop
experiment. –1.6 x
10-19 coulomb
• Thomson and
Millikan calculated
the mass of the
electron to be 9.1
x 10-28 g. This is
1/1837 the mass
of a Hydrogen
atom.
Becquerel/Curries
• Becquerel - Radioactivity
• Curie – Discovered radioactive elements of
radium and polonium
Radioactivity
1. Alpha particle – is two protons and two
2.
3.
neutrons bound together and is emitted from
the nucleus, 2+ charge, 4.0 grams, least
dangerous.
Beta particle – an electron emitted from the
nucleus 1- charge
Gamma rays are high energy electromagnetic
waves emitted from the nucleus, most
dangerous.
Radioactivity
• Alpha – large
Relatively slow
• Beta – much smaller
Relative fast
• Gamma – no mass
Pure energy
Travels at the
Speed of light
Ernest Rutherford
• New Zealander
• Discoverer of alpha,
•
•
beta & gamma
radiation.
Discovered nucleus of
atom in 1912.
Laserdisc demo – Side
2, Chapter 20
Rutherford’s Experimental Design
• Uranium alpha
•
•
•
emitter.
Slits to focus radiation
Gold foil target.
Scintillation screen of
zinc sulfide to flash
when hit.
Rutherford’s Prediction
Positive alpha particles
would go straight
through or have
minor deflections due
to the electrons
embedded in a sea of
positively charged
matter.
Rutherford’s Observations
Interpreting the Results
• Most positive alpha particles went straight through or were slightly
•
•
•
deflected.
Therefore the atom is mostly empty space.
A few positive alpha particles bounced back radically!
Thus the atom must have a large concentration of positive charge!
Rutherford’s Atomic Model
Development of the Bohr Model
• In 1913 Danish
•
physicist Neils Bohr
proposed a new model
of the atom.
Bohr’s Model explained
the emission and
absorption patterns of
light discovered by
Bunsen in flames &
lamps.
Emission Lamps
Emission Spectra
• Each element emits a unique set of bright line wavelengths.
Emission Spectra of All the Elements
• http://chemistry.beloit.edu/bluelight/movi
epages/em_el.htm
• http://jersey.uoregon.edu/vlab/elements/E
lements.html
• http://www.webelements.com/
4 Principles of the Bohr Model
1)Electrons assume only certain orbits around the
nucleus. These orbits are stable and called
"stationary" orbits.
2)Each orbit has an energy associated with it. The
lowest energy levels are close to the nucleus.
The farther from the nucleus corresponds to
higher energy levels. Electrons tend to occupy
the lowest energy levels available.
3)Light is emitted when an electron jumps from a
higher orbit to a lower orbit. Light is absorbed
when it jumps from a lower to higher orbit.
4)The quantity of energy and wavelength of light
emitted or absorbed is given by the difference
between the two orbit energies. (Quantum
Leaps!)
• With these conditions
•
•
Bohr was able to
explain the stability of
atoms as well as the
emission spectrum of
hydrogen.
Line spectra correspond
to quantum leaps
between levels of
specific energies.
Violet light corresponds
to high energy
quantum leaps while
red light corresponds to
low energy. ROYGBIV
Excited State
Ground State
Green light
emitted
Red light
emitted
Excited State
Semi-Excited State
Excited vs Ground States
• Light is absorbed when electrons jump up to
•
•
•
higher “excited” energy levels.
Light is emitted when electrons jump back down
to their lowest energy “ground” state energy
levels.
Animated Absorption & Emission
Fluorescent lights are constantly exciting gas
atoms to emit light by passing a stream of
electrons through the interior gas.
The Sun’s Spectra
• Many elements
can be identified
by their unique
lines.
• Helium was 1st
discovered in the
Sun’s (Helios)
spectrum
Emission vs Absorption
Colors Lab A. Flame Tests
NO DOUBLE DIPPING!
Asthmatics may be excused
Test 10 known compounds & 3 unlabeled to identify.
Make data table:
#
Salt
Formula
Salt
Appearance
Flame Color &
Effects
Colors Lab B. Spectral Emissions
Lamp # of Colors of
#
Lines ROYGBIV
Line Pattern
ID
Element
Comparing Atomic Models
Dalton
Picture of
Atomic
Model
Evidence
Thomson
Rutherford Bohr
Atomic & Nuclear Chemistry
Geiger Counter Demos
Sample
Humans
NaCl vs KCl
Smoke Detector
Old Fashioned
Lantern Mantle
Old Glow in the
Dark Clock
Uranium Ore
Counts per
Minute
Reason
Radioactivity (PS1 Ch26, )
Types of
Radiation
Symbol
Alpha
Beta
Gamma
a (He)
b (e-)
g
Mass
4 amu
0 amu
Charge
+2
1/1837
amu
-1
Composition 2 protons,
2 neutrons
Penetration Blocked by
paper
0 (movie)
1 electron
High energy
photon
Sheet
metal
Blocked by 1ft of
concrete or few
inches of lead
Alpha Emission
263
Sg
106
4
2
He
+
259
Rf
104
http://www.remm.nlm.gov/alpha_a
nimation.htm
• The unstable nucleus simultaneously
ejects two neutrons and two protons,
which correspond to a helium nucleus.
• The emission of gamma photons is a
secondary reaction that occurs a few
thousandths of a second after the
disintegration.
Beta Emission
14
6
C
0
-1
e
+
14
7
N
+
g
Gamma Radiation
Radioactivity Shielding Lab
Essential Question:
There are a variety of medical diagnostic
equipment which use radioactive materials
inside. What is the most efficient way for
manufacturers to cut down exposure for
patients & medical staff?
Materials:
Geiger Counter, Lead box, Uranium Ore
Sample, Ruler, Stop Watch,
Shielding Material Options:
water, paper, plastic, cardboard, glass,
ceramic tiles, aluminum foil, sheet copper
Radioactivity Shielding Lab
What variables can we change?
Distance?
Material?
Thickness?
Distance vs Radioactivity
1st Trial
Background
1cm
2cm
3cm
4cm
5cm
2nd Trial
Average
Shielding Material vs Radioactivity
Select 5
Materials
1st Trial
2nd Trial
Average
Radioactivity Lab Directions (1 of 2)
As a lab group:
Part A: Investigate the effect of distance on
radioactivity over at least 5 different levels.
1. Write an “if, then” hypothesis.
2. Write a reason for your hypothesis.
Part B: Investigate the effect of a shielding material on
radioactivity.
1. Choose your unique material to vary over at least 5
different levels.
2. Write an “If, then” hypothesis.
3. Write a reason for your hypothesis.
4. Use distances that produce as large of counts as
countable.
Safety Guidelines:
1. Always keep sample in lead box.
2. Always face opening towards the wall.
3. Rotate counters to minimize exposure.
Lab Requirements
• Determine the background radiation
• Use as our baselines the highest countable
radioactivity possible.
• At least 5 different levels for each
experiment.
Controlled Variables
Distance
• same equipment,
• distance increments,
• time,
• Positions & angles
Shielding
• same shielding
material,
• distance,
• material additions,
• time
How Organize your Data Table?
Required Elements:
• Level – distance or shielding
• Trial – 1st, 2nd, or 3rd repetition
• Counts – per minute (or variation)
• Observations – things you notice and
record verbally like sources of error.
Finish Geiger Lab – Due Friday
Pick Your Roles & Rock & Roll:
Safety officer
Set up experiments – Control distance?
Count clicks
Time experiments.
Record data
Calculate averages
Make Excel graph
Powerpoint lab report – start now.
Presentation
Recommendations for Minimizing
Radiation Exposure
Based on the findings of the class, what do you
recommend that manufacturers use to most
efficiently and effectively protect patients and
employees from unnecessary exposure to
radioactive diagnostic equipment? Write your
recommendation in full sentences. Mention at
least 2 factors.
XC How could we test to see if radioactivity
reflects off of the material used. Diagram the
set up.
Side 10 - Chapter 2 – Ancient Cultures –
Archaeology – C14 Dating
Side 10 – PET Scan – Positrons – ½ lives
Gamma rays
Geiger Lab Rubric
Presentation
Skills
Points made
clearly &
concisely
Summarizing
information
clearly.
Summarizing,
but lacking
clarity.
Reading to
audience,
lacking eye
contact or
loud voices.
Experimental All external
Design
influences
controlled as
well.
Internal
variables of
experiment
controlled
Lacking
controls on
internal
variables.
Clear
independent &
dependent
variable.
Data &
Observations
Complete set
of multiple
(>2) trials.
Complete set of One complete
2 trials for each set of trials.
experiment.
Conclusions
Accurately
Uses
interprets
experimental
results &
evidence
applies to life.
Compares
results.
Data missing
from report.
Revisits
hypothesis
Isotopes
• Atoms of a single element have the same
•
•
•
•
number of protons but may differ in neutrons.
Example 1: Carbon-12 vs Carbon-14
Example 2: Uranium-238 vs Uranium-235
Some isotopes are stable while others are
unstable and radioactive.
The STRONG NUCLEAR FORCE acts between
protons & neutrons to hold them together.
However protons will repel each other with their
mutual positive charge.
Carbon Isotopes
Isotope
Carbon –
Carbon –
Carbon –
Carbon –
Carbon –
Carbon –
Carbon –
Carbon –
9
10
11
12
13
14
15
16
Half – life
0.1265 s
19.2 s
20.38 min
Stable
Stable
5715 y
2.449 s
0.75 s
• How long does it take
400 g of each isotope
to decay to less than
1 mg?
Beanium – Average Atomic Mass Activity
7. Find the average mass of each of the 3 beanium
isotopes.
Average mass of ___ beans = subtotal mass/#of
beans
8. % Abundance of each type =
# of beans/total beans (x100 to make a %)
10. Average beanium atomic mass
= (%white x avg mass white)
+ (%black x avg black mass)
+ (%red x avg red mass)
*Convert the %s back into decimals to do #10.
Uranium Decay Series
• U238 alpha - HL
•
•
•
•
•
•
4.468e9y
Th234 beta – HL 24.10d
Pa234 beta – HL 6.70h
U234 alpha – HL
245,500y
Th230 alpha – HL
75,380y
Ra226 alpha – HL1600y
Rn222 alpha – HL
3.8325d
•
•
•
•
•
•
•
•
Po218 alpha – HL 3.10m
Pb214 beta – HL 26.8m
Bi214 beta – HL 19.9m
Po214 alpha – HL 164.3
ms
Pb210 beta – HL 22.6y
Bi210 beta – HL 138d
Po210 alpha – HL
4.199m
Pb206 Stable!
Nuclear Reactions
• Radioactivity results from changes in
atomic nuclei.
• Fission – splitting of a large nucleus into
smaller pieces releases energy.
• Fusion – small nuclei join to make a larger
nucleus and release energy. (PS1, Ch25)
• Energy is released when a small amount
of mass converts to energy as E = mc2.
Fusion of Hydrogen Isotopes
• At high temperatures
and pressures, 2
nuclei may collide and
form a bigger nucleus.
• This example produces
helium and a stray
neutron.
• Stars are fueled by the
energy released by
fusion which also
builds atoms of
increasing sizes in
their cores.
Fission of Uranium
• A neutron splits the
•
•
•
nucleus.
The fragments include:
– 2 different smaller
atoms,
– 3 more neutrons.
The 3 neutrons can split
more atoms.
If every fission splits 3
more atoms, the
reaction will multiply out
of control!
Nuclear
Chain
Reaction
Nuclear Equations
• Styrofoam Demos
• Alpha Decay – releases a helium nucleus.
• Beta Decay – a neutron converts to a
proton and releases an electron.
• Assignment: Uranium Decay Series
Nuclear Warheads
Chernobyl Nuclear Disaster
Nuclear Equations Problems
1.
2.
3.
4.
5.
U–238 does alpha decay in nuclear reactors.
Am-241 does alpha decay in smoke alarms.
Tc-98 does beta decay in medical exams.
C–14 does beta decay in carbon dating.
The Curies used Ra-226 which does alpha
decay.
6. Co–60 does beta decay in food irradiation.
7. Th-232 does alpha decay in camp lanterns.
8. P-35 does beta decay in DNA studies
(Place isotopes activity in Outbox)
Nuclear Equations Quiz
1.Write the nuclear
equation for the alpha
decay of Iodine 131.
2.Write the nuclear
equation for the beta
decay of cobalt 60.
½ Lives Activity
• Obtain a set of “radioactive” blocks. Notice that each one
•
•
•
•
has a mark on one side – either a, b or g.
Roll the collection of blocks onto your table. Each time you
roll, remove any blocks that come up a, b or g.
Count and record the remaining blocks. Roll the remaining
blocks repeatedly 20 times and complete the chart below.
Enter your group data into the excel file.
Make graphs of Time(minutes) Remaining Atoms for both
individual & class averages. **Use “exponential” rather than
“linear” trendlines.
Roll
(minutes)
Remaining
Atoms
Class Average
½ Lives Activity Questions
1. How do your lab pair results compare
with the class average results?
2. Use the class average results and
compute the 1st ½ life, 2nd ½ life,
average ½ life.
3. What importance do ½ lives have to
society?
(dating, medical uses, wastes)
½ Lives
• Each radio-isotope decays at a characteristic
•
•
•
•
rate.
The decay rate is determined by the time that it
takes for ½ of the radio-isotope nuclei to break
down by fission.
Each ½ life reduces the remaining number of
radioactive atoms by ½.
The number remaining approaches but never
reaches zero.
Example: Iodine 131 has a ½ life of 8 days.
How much of 1.00 gram sample would remain
after 24 days?
Solving ½ Life Problems
Masses:
• STARTING
MASS
• Divided in ½
the # of half
lives.
• ending mass
# of half
lives
Times:
• Time for 1 half
life (HL)
• Total time
elapsed (T)
• T = HL*(#)
• HL = T/#
• # = T/HL
½ Life Problems
1. If you have $1 million dollars and every 2
seconds it decreases by 1/2, how long will it
take until you are penniless?
2. If a sample of a fossil mammoth has 1/8th the
amount of carbon 14 as it would today, how
old must the fossil be? (1/2L C14 = 5715
years.
3. If a rock contained 1.2 g of potassium 40
when it formed, how many grams remain after
4 billion years. (1/2L K40 = 1.33E9 y)
Asmt: P780 #1&2, P803 #24&25
More ½ Life Problems
4. If a sample of radioactive isotope has a half-life of 1 year,
how much of the original sample will be left at the end of
the second year? The third year? The fourth year?
5. The isotope cesium-137, which has a half-life of 30
years, is a product of nuclear power plants. How long
will it take for this isotope to decay to about onesixteenth its original amount?
6. Iodine-131 has a half-life of 8 days. What fraction of the
original sample would remain at the end of 32 days?
7. The half-life of chromium-51 is 28 days. If the sample
contained 510 grams, how much chromium would
remain after 56 days? How much would remain after 1
year?
½ Lives Quiz
1. A sample of a radioactive isotope with an
original mass of 8.00g is observed for 30 days.
After that time, 0.25g of the isotope remains.
What is its half-life?
2. The starting mass of a radioactive isotope is
20.0g. The half-life period of this isotope is 2
days. The sample is observed for 14 days.
What PERCENTAGE of the original amount
remains after 14 days?
Health Physics Society
• http://hps.org/publicinformation/ate/q754.html
• Q:What are some health effects of the element uranium?
• A:The toxicity of uranium has been under study for over 50 years,
including life-span studies in small animals. Depleted uranium and
natural uranium both consist primarily of the uranium isotope 238U.
They are only very weakly radioactive and are not hazardous
radioactive toxicants, but uranium is a weak chemical poison that
can seriously damage the kidneys at high blood concentrations.
Virtually all of the observed or expected effects are from
nephrotoxicity associated with deposition in the kidney tubules and
glomeruli damage at high blood concentrations of uranium. The
ionizing radiation doses from depleted and natural uranium are very
small compared to potential toxic effects from uranium ions in the
body (primarily damage to kidney tubules).
Modern Atomic Theory
Quantum Mechanical Model
(Electron Cloud Model)
Electrons & Standing Waves
1. Electrons don’t move in straight lines;
they move as waves.
2. Electron microscopes allow us to see flies
eyes since electron wavelengths are
shorter than visible light waves.
3. Electrons orbiting a positive nucleus
settle into low energy standing waves
4. Demo – Standing waves
Orbitals
1. Electron wave orbits are
too complicated to
track.
2. Chemists describe their
probable location as
clouds.
3. Orbitals are defined as
the space they occupy
90% of the time.
4. Demo: Electrons
occupy orbitals like fan
blades
Orbital Demos
1. Electrons move so fast they occupy
space like fan blades!
2. The most stable patterns for electron
wave motions are standing waves!
3. *Electrons move fastest passing the
nucleus and spend little time there.
http://galileoandeinstein.physics.virginia.edu
/more_stuff/flashlets/Slingshot.htm
1. Orbital Diagrams
2. Video – CheMedia Side 2, Chapter 23
F orbitals
• Start at the fourth energy level
• Have seven different shapes
• 2 electrons per shape for a total of 14
electrons.
F orbitals
Electron Orbitals
Type
Shape
Set
1st Occur
S
Spherical
1
Level 1
P
Dumb-bell
3
Level 2
D
Cloverleaf
5
Level 3
F
8 Lobed
7
Level 4
Electron Configurations
• Orbitals can hold 2 electrons each.
• Lowest energy orbitals fill first.
• Electrons repel and occupy separate
orbitals on the same energy level if
possible.
• Orbital Packing Key:
• 1s22s22p63s23p64s23d104p65s24d105p6…….
• Animated Electron Configurations
Orbital filling table
Electron Configurations vs Pictures
1 H 1s1
-
+
Electron Configurations vs Pictures
1 H 1s1
2 He 1s2
-
++
-
Electron Configurations vs Pictures
1 H 1s1
2 He 1s2
3 Li 1s22s1
-
++
+ -
Electron Configurations vs Pictures
1 H 1s1
2 He 1s2
3 Li 1s22s1
4 Be
-
1s22s2
-
++
++ -
Electron Configurations vs Pictures
1 H 1s1
2 He 1s2
-
3 Li 1s22s1
4 Be
- ++ +
++ -
1s22s2
5 B 1s22s22p1
-
Electron Configurations vs Pictures
1 H 1s1
2 He 1s2
-
3 Li 1s22s1
- +++
++
+ -
4 Be 1s22s2
5 B 1s22s22p1
6 C 1s22s22p2
-
-
Electron Configurations vs Pictures
7N 1s22s22p3
1 H 1s1
2 He 1s2
-
3 Li 1s22s1
- +++
++
+
+ -
4 Be 1s22s2
5 B 1s22s22p1
6 C 1s22s22p2
-
-
Electron Configurations vs Pictures
7N 1s22s22p3
1 H 1s1
2 He 1s2
3 Li 1s22s1
4 Be 1s22s2
5 B 1s22s22p1
6 C 1s22s22p2
8O 1s22s22p4
- + +++
++
+
+ -
-
-
Electron Configurations vs Pictures
7N 1s22s22p3
1 H 1s1
2 He 1s2
8O 1s22s22p4
-
3 Li 1s22s1
-
- + +++
++
+
+ -
4 Be 1s22s2
5 B 1s22s22p1
6 C 1s22s22p2
9F 1s22s22p5
-
-
-
Electron Configurations vs Pictures
7N 1s22s22p3
1 H 1s1
2 He 1s2
3 Li
8O 1s22s22p4
-
1s22s1
-
- + +++
++
+
++ -
4 Be 1s22s2
5 B 1s22s22p1
6 C 1s22s22p2
-
-
9F 1s22s22p5
-
10Ne 1s22s22p6
Electron Configurations vs Pictures
7N 1s22s22p3
1 H 1s1
2 He 1s2
3 Li
-
1s22s1
-
- + +++
++
+
++ -
4 Be 1s22s2
5 B 1s22s22p1
6C
8O 1s22s22p4
-
1s22s22p2
-
9F 1s22s22p5
-
10Ne 1s22s22p6
-
11Na
1s22s22p63s1
Electron Configurations vs Pictures
-
-
-
- + +++
++
+
++ -
-
-
Electron Configurations vs Pictures
-
-
-
- + +++
++
+
++ -
-
-
Electron Configurations vs Pictures
-
-
-
- + +++
++
+
++ -
-
-
Examples:
1. Write the electron configuration & draw
an atom of fluorine.
Asmt: Write electron configurations of
elements 1,5,9,13,17,21,25,29.
Photoelectric Effect & Solar Energy
• http://www.walter-
fendt.de/ph14e/photoeffect.htm
• http://phet.colorado.edu/new/simulations/
sims.php?sim=Photoelectric_Effect
• http://www1.eere.energy.gov/solar/photo
electric_effect.html
• http://www.electronsolarenergy.com/reso
urces.htm
Tuesday 11/27/07
Prep:
1.
2.
See Neil about Periodic Table Activities
Determine Periodic Table book assignment
Class:
Periods 1 & 3
DMA: What element corresponds to the configuration [Kr]5s24d105p5?
1. Take & correct quiz
2. Periodic Table Activity
Asmt: Page 163 #1-4, page 173 #1,3, page 185 #2
Plan: Meet with POD
Periods 4-6
Library Utopia Project
Afterschool:
1. Grade Poster Projects
2. Contact National Boards about appeal of Active Inquiry
3. Go to Wells Fargo
1.
2.
Deposit checks, get new registers!
Provide mortgage documents
Orbital Animations
• Chemedia Laserdisc Demo – Side 2,
Chapter 23
• http://www.colby.edu/chemistry/OChem/
DEMOS/Orbitals.html
Electron Configurations Quiz 1
1. Write the full electron configuration & draw the
2.
3.
atom for nitrogen, N – atomic number 7,
atomic mass 14.01.
Write the full & Noble Gas electron
configurations for nickel, Ni – atomic number
28.
Identify the element with the Noble Gas
electron configuration of [Ar]4s23d6.
Explain how you know.
Electron Configurations Quiz 2
1. Write the electron configuration & draw
an atom of oxygen.
2. Write the complete and Noble Gas
configurations for arsenic, As.
3. Identify the element that approximately
matches [Xe]6s25d104f146p2 & explain
how you know.
Periodic Table Activity
Thursday 11/29/07
Prep:
1. Grade fireworks posters.
Class:
P1-3
DMA: What principle determines which elements are in the same vertical column?
Due: Page 163,173,185, Fill in blanks?
1.
Fill in blanks Periodic Table, 1 part at a time
2.
Notes on Development of Periodic Table
Asmt: Shade sections of 9 overlapping sections of Periodic Table (pages 164-7)
Plan:
1.
Finalize POD meeting plans & Sliding Scenario pieces.
2.
Grade Fireworks posters.
P4-6
DMA: Electron Configurations Quiz 2
1.
Grade Quiz
2.
Periodic Table Card Puzzle
Asmt: Asmt: Shade sections of 9 overlapping sections of Periodic Table (pages 164-7)
After School:
1.
Grade fireworks posters
2.
Thursday chores at home plus piano practicing.
3.
Left overs, chips to Men’s group.
Development of the Periodic Table (1 of 2)
• Periodic Law – When elements are
arranged in increasing atomic number,
their chemical & physical properties show
a periodic pattern.
• Dobereiner grouped the elements into
triads with similar chemical properties.
• Newlands arranged the elements by
increasing atomic mass and observed the
Law of Octaves where elements of similar
properties occurred every 8th element.
Development of the Periodic Table (2 of 2)
• Mendeleev arranged the elements by increasing
•
•
•
mass & similar properties in 1872.
Mendeleev suggested that atomic masses that
were out of line with the similar properties
needed to be remeasured.
Mendeleev accurately predicted the existence
and properties of elements yet to be discovered.
Moseley discovered a pattern in the spectral
lines of elements which corresponded to the
atomic number and number of protons.
Periodic Table Patterns
• http://www.sciencebyjones.com/periodic_t
able1.htm
• http://environmentalchemistry.com/yogi/p
eriodic/#Chemical%20elements%20sorted
%20by
• Can use the one above to find the
patterns & then explain them.
Observing Element Samples
1. Use your blank periodic table with trends
of electron configurations.
2. Observe 2 samples from each of the 9
sets around the room.
3. For each sample, record the symbol in
the correct box plus 2 words to describe
the appearance of the sample.
Monday 12/2/07
• Periodic trends – atomic radius, ionization
energy, electronegativity
• Analyze data & graphs, Explain trends
Patterns of Electron Configurations
Vertical Patterns
Horizontal Patterns
Same number and type
of valence electrons.
Same kernel across
Energy level rises for
each row.
The kernel is the
previous noble gas
Highest energy level is
the same across a row.
Patterns of Electron Configurations
• Vertical Patterns
• Same number and
•
type of valence
electrons.
Energy level rises for
each row.
• Horizontal Patterns
• Same kernel across
• The kernel is the
•
previous noble gas
Highest energy level
is the same across a
row.
Periodic Patterns
: :
[x]
+4
-4
-3
: :: :
:
+3
:
[x] [x]
:
+2
:
+1
:
:
X
:
. X :Be
-2
: :
s2
: :
H.
s2p6
2p3 s2p4 s2p5 :He
2
1
2
2
s
sp sp
.
.
:X. :C. :N. . :O. . :F. : :Ne:
.
. Al . X. . X. . . X: : X. : X :
: :
s1
-1
[:x:] [:x:] [:x:]
Ion formation: Loss (oxidation) or gain (reduction) of electrons
Periodic Trends
• Trends in atomic radius, ionization energy, &
•
•
•
•
electronegativity are determined by:
The number of energy levels present.
The attraction between the positive nucleus and
the outer shell electrons.
Interfering “shielding” by electrons on inner
shells.
How close an atom is to completing the stable
octet of outer “valence” electrons.
Atomic Radius (1 of 3)
• Alkali metals are the largest atoms.
• Noble gases are the smallest atoms.
Atomic Radius (2 of 3)
Atomic radius
trends:
1) Atomic radius
increases
down a group
or column.
2) Atomic radius
decreases
across a
period or row.
Atomic Radius (3 of 3)
How do we explain the trends?
1. Atomic radius increases down a group:
•
•
Each row adds an energy level.
Interior electrons interfere with attraction of
valence electrons toward the nucleus
“shielding effect”
2. Atomic radius decreases across a row
even while the atomic number increases:
•
While in the same energy level, the nucleus
becomes more positive & attractive.
• Ionization – Removal of electrons produces +
•
•
•
charges & shrinks radius.
http://hogan.chem.lsu.edu/matter/chap26/anim
ate2/an26_017.mov
Animated Ionizations Change Radii Across
periodic table.
http://www.chem.iastate.edu/group/Greenbowe
/sections/projectfolder/flashfiles/matters/periodi
cTbl2.html
Ionization Energy (1 of 4)
• Ionization energy is
•
the energy required
to remove a
negative electron
and leave an atom
with a positive
charge – as an ion.
Occurs in solar
cells, geiger
counters & smoke
detectors with
Amerecium 241
Ionization Energy (2 of 4)
• Alkali metals lose their electrons most easily.
• Noble gases hold their electrons most tightly.
Ionization Energy (3 of 4)
• Removing an
•
electron
becomes more
difficult across
a row.
Removing
electrons
becomes easier
down a column.
Ionization Energy (4 of 4)
• Removing electrons is more difficult across a
•
•
row as the nuclear attractions become stronger.
Removing electrons is easier down a column as
each additional energy level increases the
distance from the nucleus and weakens the
nuclear attraction.
Repulsive shielding by interior electrons also
decreases the attraction for each added level.
Electronegativity (1 of 3)
• Electro-
negativity is
the ability of
an atom to
attract
electrons
that are
shared in a
covalent
bond.
Electronegativity (2 of 3)
• What are the trends in electronegativity?
Electronegativity (3 of 3)
• Electronegativity
•
•
increases up & to
the right.
This trend
corresponds to
stronger
attractions to the
nucleus.
Less shielding
effect strengthens
attractions to the
nucleus in upper
rows.
Periodic Patterns Quiz
Atomic Radius Question – What is the size
surprise? Why does it occur?
Ionization Energy – Why are the lowest
ionization energies in the bottom left?
Electronegativity – Arrange each set of
atoms in order from least to greatest
electronegativity: Mg, Ba, Sr; Cl, F, I; Fe,
K, Br
Periodic Patterns of Reactivity
• Choose an element from the periodic
table.
• Predict how you think it will react with air,
water, acids or bases.
• Observe the laserdisc video.
• Record the reactivity on a 1R-10R scale.
• Examine no more than 3 per group.
• Identify patterns of reactivity.
Comparing Periodic Groups
Group
Common
Valence
Electrons
Common
Ionic
Charges
Properties
Sources of 2 –
How obtained
Uses of 2
elements of
Group
Alkali
S1
+1
Soft metals,
Explode in H2O
Electrolyze salts
Na – table salt
K - gatorade
Alkaline
Earth
Transition
Boron
Carbon
Nitrogen
Oxygen
Halogens
Noble
Gases
Comparing Periodic Groups
Group
Valences
Ions,
# of Bonds
Properties
Sources of 2 –
How obtained
Uses of 2
elements min
Alkali
S1
+1, ionic
Soft metals,
explosive
Electrolyze salts
Na – table salt
K – gatorade
Alkaline
Earth
S2
+2, ionic
Soft, highly
reactive
Electrolyze salts
Ca – bones,
Mg – flash bulbs
Transition
S2d1 –
s2d10
Various charges
+2,+3, +4
Hard metals,
w/ varying
resistance
Mined &
extracted from
ores
Iron in steel,
Gold jewelry
Boron
S2p1
+3, (or 3 bonds)
Nonmetals &
metals
Extracted from
bauxite ore
Al - cans
Carbon
S2p2
+ or – 4, 4
bonds
Nonmetals to
metals
Common in life,
rocks & ores
C – pencils, Si –
chips, Pb – wts
Nitrogen
s2p3
-3, 3 bonds
Non-metals,
semi-metals
N from air, P from
phosphates
Fertilizers
Oxygen
S2p4
-2, 2 bonds
Non-metals to
metals
O from air, S
mined
Breathing, make
sulfuric acid
Halogens
S2p5
-1, 1 bond
Reactive
Nonmetals
Electrolyze salts
Cl – bactericide
F - toothpaste
Noble
Gases
S2p6
0, 0 bonds
Unreactive
gases
Isolated from air
He – balloons
Ar – light bulbs