Transcript Chemistry catalysts - Laurens County School District

CHEMISTRY CATALYSTS
Fall 2011 – Week 6 (Atomic Structure & Nuclear)
Catalyst (5 min)
9/17/12 Atomic Models
 EQ: How can I model the parts of an atom?

1.
Calculate the numbers of protons, neutrons,
and electrons in these three isotopes.
 Helium
–4
 Neon - 21
2.
Draw Bohr models of these three isotopes.
Review

Question 1
1.
How many protons, neutrons,
and electrons does Neon have?
Question 2
Draw a Bohr model of an
oxygen atom?

Question 3
Who
discovered electrons?
Question 4

How many protons, neutrons,
and electrons does Oxygen-15
have?
Catalyst (5 min)
9/14/11 Nuclear Decay
 EQ: How does the nucleus of an atom
change during decay?

 What
do you think when you hear the
word nuclear?
 Is it a positive word or a negative word?
 Write 4-6 detailed sentences describing
your reaction.
NUCLEAR DECAY
When it all just falls apart…
What is Nuclear Decay?
Nuclear decay occurs when the
nucleus of an atom is unstable.
Particles and/or energy are
emitted (given off) from the
nucleus to help stabilize it.

Nuclear Foldable (Front)



alpha
beta
gamma
Nuclear Foldable (Inside)
Composition:
Charge:
Mass:
Penetration:
Shielding:
Symbols:
Alpha Particles ()






Made of 2 protons & 2 neutrons
Charge = +2
Mass = 4 amu
(Heavy and slow particles)
Low penetrating power
Can be blocked by a single sheet
of paper
Symbols used:
4
2
He
4

2

Alpha Decay


Alpha decay occurs when a large nucleus ejects
two protons and two neutrons (an alpha particle).
The results are a mass change of 4 amu and a more
stable nucleus.
Beta Particles ()






Made of 1 electron
Charge = -1
Mass = 1/1840 amu
(Fast and light particles)
Medium penetrating power
Can be blocked by thin metal like
aluminum foil or thin wood
Symbols used:
 1
0
 1e
0
Beta Decay


Beta decay occurs when a neutron splits into a
proton and an electron.
This results in no change in mass, but the isotope
does become a different element.
Gamma Rays ()






Made of waves, not particles
Charge = 0
Mass = 0
High penetrating power
Can be mostly blocked by
using 10cm or more of solid
lead, but never completely
Symbol used:

0
0
Gamma Ray Radiation


Gamma radiation is produced by a nucleus in the
“excited state.” When a nucleus has too much energy, it
can release some of it as gamma radiation.
The result of this is no change in mass, charge, or
composition – just a more stable nucleus with less energy.
1
1
1
1
2
2
2
2
3
3
3
3
Determining Charge of Radiation
Shielding Radiation
Beta ()
shielding
Alpha ()
shielding
Gamma ()
shielding






Warm Up
9/15/11 Nuclear Decay
 EQ: What is the half-life of a radioactive
isotope?

 You
have three radioactive cookies:
emits  particles.
 One emits  particles.
 One emits  particles.
 One
 You
must eat one, hold one in your
hand, & hold one in your pocket.
 Which cookie goes where? Explain.
Nuclear Cookies
Math Equations
8 = 12
4 + ___
6 +4
10 = ___
22 +
12 + 9 = ___
-1
Chemistry Equations
Math uses an = sign.
Chemistry uses an .

H2 + O2  H2O
reads “Hydrogen plus oxygen
yields water.”
Example:
 - decay
238
92


U
234
90
Th + He
4
2
Add this equation to your foldable.
Note that the left side and right side are equal for
the top number and bottom numbers.
 - decay
14
6


C  N+ e
14
7
0
1
Add this equation to your foldable.
Note that the left side and right side are equal for the
top number and bottom numbers.
 - decay
27
13


Al 
27
13
Al + 
0
0
Add this equation to your foldable.
Note that the left side and right side are equal for the top
number and bottom numbers.
Review Nuclear Equations

Alpha decay of Uranium-235.
235
92
U

Th
He
Beta decay of Uranium-235.
235
92
U

231
90
4
2
235
93
0
-1
Np
e
Gamma decay of Uranium-235.
235
92
U

0
0
235
92
U
Examples of Nuclear Equations
Xe
129
54
Po
212
84
Es
243
99
52
22
Ti
How to Play Nuclear Decay



Decide who goes first. This person rolls both dice.
Starting with Am-241, all players write an equation
for , , or  decay that matches the roll on the die.
Players earn points for correct answers
 The
roller earns the # of points from the numbered die.
 Everyone else earns 1 point for any correct answer.
 No points for incorrect answers.


Keep going until you run out of protons or neutrons.
Highest score wins!
Example


Suppose I rolled these dice.
I write this equation.
Correct!

Am e Cm
0
1
241
96
3
3 points 
Group member A writes:
Incorrect!

241
95

241
95
Am e Pu
0
1
241
94
0 points 
Group member B writes:
Correct!
241
95
Am e Cm
0
1
241
96
1 point 
How to Play Nuclear Decay



Decide who goes first. This person rolls both dice.
Starting with Am-241, all players write an equation
for , , or  decay that matches the roll on the die.
Players earn points for correct answers
 The
roller earns the # of points from the numbered die.
 Everyone else earns 1 point for any correct answer.
 No points for incorrect answers.


Keep going until you run out of protons or neutrons.
Highest score wins!
Catalyst (5 min)
9/16/11 Half Lives
 EQ: What is the half-life of a radioactive
isotope?

Write
equations for:
 Alpha
decay of Np-237
 Beta decay of Np-237
 Gamma decay of Np-237
Use
your foldable for help!
What is a half-life?

A half-life is the amount of time it takes for half of
the amount of a substance to decay.
 For
example:
 241Pu has a half-life of 14 years. Suppose we start
with 100 grams of 241Pu
 14
years later, we have 50 grams
 28 years later, we have 25 grams
 42 years later, we have 12.5 grams…

Band of Nuclear Stability & Half-Lives