Download The Band of Stability

Name: _____________________________
Date: ______________________________
Class: ______________________________
Nuclear Chemistry
Chemistry Honors
The Band of Stability
Introduction:
Radioactivity is the spontaneous emission of radiation by nuclei. Radioactive decay changes the nature
and identity of an atom’s nucleus. This occurs for a specific reason. Elements from hydrogen to lead
(atomic numbers 1-82) have stable isotopes in which the tendency of protons to repel one another is
overcome by attractive nuclear forces. The forces require ideal distances between the protons. The
neutrons help create these ideal distances. If there are too many or too few neutrons, the nucleus
becomes unstable.
If an atom has more than 82 protons in the nucleus, there is no arrangement of neutrons that can
produce more than attractive forces than repulsive forces. Therefore, all isotopes of elements beyond
lead are radioactive. Their only route to stability is to first reduce the overall size of the nucleus by losing
large particles.
Part I: Create a Band of Stability
You will be graphing the proton and neutron numbers for some isotopes that are known to be stable.
-
Using an entire side of a piece of graph paper, draw a vertical “y” axis and label it
“Neutrons.” Draw a horizontal “x” axis and label it “Protons.”
Scale the y-axis so that it goes from 0 to 150.
Scale the x-axis so that it goes from 0 to 100.
On a piece of loose leaf, complete the following table.
** Remember! This is only a small portion of the list of stable isotopes.
-
Plot the points from the table that correspond to the axes on your graph.
Draw a bold, smooth curve through the points. (As smooth as possible.)
Part II: Unstable Isotopes
-
On a piece of loose leaf, complete the following table.
** Remember! This is only a very small portion of the list of unstable isotopes.
-
Plot the points from the table that correspond to the axes on your graph. Label each point
with the identity of the isotope that it represents.
**Elements that fall outside of the band of stability cannot exist long enough to be recognized as
elements.
** The elements that are found in the middle of the band of stability have a very stable nucleus.
Name: _____________________________
Date: ______________________________
Class: ______________________________
Chemistry Honors
Nuclear Chemistry
Transmutations
Part III: Transmutations
Now that you have learned about the band of stability and what it means, you are ready to learn about
the different types of radioactive decay.
Go to the following video and fill in the answers below. The video is about 10 minutes long.
https://www.youtube.com/watch?v=KWAsz59F8gA
1. A transmutation occurs when an atom ______________________________________________
______________________________________________________________________________
______________________________________________________________________________.
2. Transmutations occur because atoms need to be __________________________.
3. What causes an atom to be unstable?
4.
An atom of radium (Ra) becoming an atom of radon (Rn) is an example of
______________________________ or _________________________________.
5. The half-life of an element is _______________________________________________________
______________________________________________________________________________
______________________________________________________________________________.
Example 1:
Polonium-214 has a relatively short half-life of 164 seconds. How many seconds woul it take for
8.0 g of this isotope to decay to 0.25 g?
Example 2:
By approximately what factor would the mass of a sample of copper-66 decrease in 51 minutes?
The half-life of copper-66 is 5.10 min.
Common Types of Radioactive Decay
1. Alpha Decay
Can be described by:
-
The nucleus of an atom splits into two parts
The alpha particle is emitted from the nucleus
The nucleus that is left behind now has an atomic number reduced by 2 and its mass
number reduced by 4. (2 protons and 2 neutrons were emitted
Write the symbol for an alpha particle using isotopic notation in the space below.
Here is a typical alpha decay equation: Fill in the blank space below.
222
88𝑅𝑎
→
+ 218
86𝑅𝑛
- Alpha radiation can be blocked by _________________________________________________
______________________________________________________________________________.
2. Beta Decay
Can be described by:
-
The emission of an ____________________.
Write the symbol for the particle here 
-
The atomic number goes up by one and the mass number remains unchanged.
A neutron inside the nucleus of an atom breaks down into a ___________________ and an
___________________ which is emitted.
Here is a typical beta decay equation: Fill in the blank space below.
14
6𝐶
→
+ 147𝑁
** Beta particles have less charge than alpha particles and much less mas. Consequently, beta particles
are more penetrating! While they cannot be stopped by a piece of paper they can be stopped by
_____________________________ or ______________________________.
3. Gamma Radiation
Can be described by:
-
-
The emission of _____________________ only.
Gamma ray- a high energy photon emitted by a radioisotope; nuclei can emit gamma rays
by themselves, or the emission of energy can accompany the emission of an alpha or beta
particle.
Can the emission of a gamma ray change the atomic number or mass number of an
element?
Write the symbol for gamma radiation here 
** Gamma rays are extremely high energy and can be very dangerous!
-
This energy can be released as
o
o
o
o
NOTE: The terms alpha, beta, and gamma radiation may also appear as alpha, beta, and gamma decay.
Additional Nuclear Reactions
You will also be responsible for knowing the following nuclear reactions.
4. Positron Decay
Positron decay is the mirror image of beta decay and can be described by:
-
The emission of a positron (a particle with the mas of an electron but a positive charge).
Something inside the nucleus breaking down causing a proton to become a neutron.
The atomic number goes down by one and the mass number remains unchanged.
-
0
The symbol for a positron is: +1
𝑒
Here is a typical positron decay equation
23
12𝑀𝑔
→
23
11𝑁𝑎
+ +10𝑒
5. Electron Capture
Can be described as:
- An electron from the closest energy level falls into the nucleus, which causes a proton to
become a neutron.
- The atomic number goes ___________ by one and the _____________ ______________
remains unchanged.
Here is a typical electron capture equation:
81
36𝐾𝑟
+
0
−1𝑒
→
81
35𝐵𝑟
What is the distinct difference between electron capture and the other types of radiation?
Practice
1. Classify each of the following nuclear reactions by particle and type of radiation (decay or
capture). e.g. alpha decay
a.
13
7𝑁
b.
238
90𝑇ℎ
→
c.
238
90𝑇ℎ
→ 42𝐻𝑒 + 234
88𝑅𝑎
d.
238
90𝑇ℎ
+
→
0
−1𝑒
+ 138𝑂
0
+1𝑒
0
−1𝑒
+ 238
89𝐴𝑐
_______________________________________
_______________________________________
_______________________________________
→ 𝛾 + 238
89𝐴𝑐 _______________________________________
Name:___________________________
Chemistry Honors
Date:__________________Period:____
Nuclear Decay Worksheet
1. Using the figure to the right, write the reaction equations represented by letters A, B, and C.
This figures shows the decays that uranium-238 undergoes to become lead-206.
A: _________________________________________
B: _________________________________________
C: _________________________________________
2. Nuclear decay takes time. This time is measured in half lives. Explain the concept of a half life.
3. An isotope of cesium (cesium-137) has a half-life of 30 years. If 1.0 mg of cesium-137
disintegrates over a period of 90 years, how many mg of cesium-137 would remain?
4. In 5.49 seconds, 1.20 g of argon-35 decay to leave only 0.15 g. What is the half-life of argon-35?
5. Selenium-83 has a half-life of 25.0 minutes. How many minutes would it take for a 10.0 mg
sample to decay and have only 1.25 mg of it remain? How many half-lives is this?
Nuclear Equations
Part I: Complete the nuclear reaction equations below. Then classify them by particle and type (decay
or capture).
1.
212
84𝑃𝑜
→ 42𝐻𝑒 + _______
2.
142
61𝑃𝑚
3.
218
84𝑃𝑜
+ _______ →
→
0
−1𝛽
142
60𝑁𝑑
+ _______
4. 74𝐵 → _______ + 73𝐿𝑖
classify: __________________________
classify: __________________________
classify: __________________________
classify: __________________________
5.
22
11𝑁𝑎
6.
238
92𝑈
→ _______ + ______ + _______
alpha and gamma decay
classify: __________________________
7.
37
18𝐴𝑟
+ ______ →→ _______
classify: __________________________
+ _______ →
22
10𝑁𝑒
classify: __________________________
Part II:
1. Write the nuclear equation for the release of a beta particle by lead-210.
2. Write the nuclear equation for the positron decay by thorium-232.
3. Write the nuclear equation for the gamma decay of cerium-144.