NUCLEAR CHEMISTRY
1. What determines which element an atom is?
Number of proton determines
2. a) How does an atom of one element change into an atom of a different element?
Explain.
When number of protons are changed.
b) What causes that change in an atom?
Radioactive decay
c) What kind of process is that?
Nuclear change
d) What is the difference between a physical change, a chemical reaction, and a
nuclear reaction?
Physical change occurs in physical structure.
Chemical structure of substance is changed.
The chancing occurs in the nucleo of atom.
−27
3. The mass of a 238
kg. Follow the steps below to find the
92𝑈 nucleus is 395.2138 × 10
energy that binds together the nucleons of 238
92𝑈 into a nucleus
a) How many protons does the 𝟐𝟑𝟖
𝟗𝟐𝑼 nucleous have?
92
Find the mass of these protons. (The mass of one proton= 1,6726 × 𝟏𝟎−𝟐𝟕 kg)
92 × 1,6726 × 10−27 = 153,8792 × 10−25
b) How many neutrons does the 𝟐𝟑𝟖
𝟗𝟐𝑼 nucleus have?
146
Find the mass of these neutrons. (The mass of one neutron = 1,6749 × 𝟏𝟎−𝟐𝟕 )
244,5354 × 10−27
c) Find the total mass of these nucleons.
398,4146 × 10−27
d) What is the difference in mass between the total mass you found in part c) and the
−𝟐𝟕
mass of the 𝟐𝟑𝟖
kg?
𝟗𝟐𝑼 nucleus, which is 395,2138 × 𝟏𝟎
3,2008 × 10−27 kg
e) Calculate the energy in joules that was given off when the U – 238 nucleus was
formed.
E = m × 𝑐2
E = 2,88072 × 10−10 joule.
4. The energy given off when the uranium nucleus was formed is called the binding
energy of the nucleus.
a) Find the binding energy per nucleın of a 𝟐𝟑𝟖
𝟗𝟐𝑼 nucleus.
1,210386 × 10−12
b) Convert the binding per nucleon from joules into units of megaelectron volts
(MeV). (1 joule = 6,25 × 𝟏𝟎𝟏𝟐 MeV)
7,5649 MeV
c) When two protons come together, vone proton can change into a neutron. The
proton and neutron can then bind together to form one deuterium nucleus. For
each deutrium nucleus formed, 3,52 × 𝟏𝟎−𝟏𝟑 joules of energy is given off. What is
this energy called?
Binding energy
d) Calculate the number of electrons volts (eV) in 3,52 × 𝟏𝟎−𝟏𝟑 joules. (Hint:1 eV = 1,6
× 𝟏𝟎−𝟏𝟗
2,2 × 106 eV / nucleon
e) How many megaelectron volts (MeV) is this?
2,2 MeV
f) How many MeV is this per nucleon?
1,1 MeV
5. The figure on the graph the binding energy per nucleon of the most stable nucleus of a
given mass number ( that is, the isotope of each element with the largest binding
energy) versus the mass number of that nucleus. The mass number is the total number
of nucleons in a nucleus.
A. According to the binding energy graph above, the nucleus of which element
has the most binding energy?
Fe
B. Why is this nucleus also the most stable?
Binding energy per nucleon is higher in Fe.
C. Which is the least stable heavy element on this graph? Why is it least
stable?
Uranium is the least stable heavy element. Being the heaviest one makes it
unstavle.
6. The graph below shows the number of neutrons versus the number of protons for
stable elements.
a) Find the slope of this line.
1
b) What does the straight line present?
Expected ratio
c) What does the group of points that form a curved line show?
Curves line shows that while the number of protons increases the number of
neutrons increase more than that.
7. a) A deuteron nucleus consists of a neutron and a proton, but the formation process
started with two protons. What must have happened to one of the protons?
Pozitron emission
b) What can happen to a nucleus with 83 or fewer protons that has too few neutrons?
Pozitron emission
c) What can happen to a nucleus with 83 or fewer protons that has too many
neutrons?
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