ci2.2 nuclear reactions

8/2/2019 CI2.2 Nuclear Reactions

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Nuclear Processes



In chemical reactions, electronsin atoms are responsible for

bonds forming and being

destroyed.

The identity of the atomsinvolved does not change



This is not true for nuclearprocesses because;

These reactions involve the

protons and neutrons in the

nucleus



There are two types of nuclearreaction

Fission and Fusion Reactions



Fission Reactions

• Involve a nucleus collapsing to form a

smaller nucleus

• Usually involve atoms with large nucleii

such as the Lathanides and Actinides

• They produce , and emissions.



Fusion Reactions

• These involve nucleii joining together to

make larger ones.

• These type of reactions are what go on

inside stars and provide the energy which

make them shine.



The particle

• Consists of 2 protons

and 2 neutrons

• Is emitted from anucleus during radio

active decay

• Is the most destructive

radiation because it

ionises atoms it bumps

into



An decay reaction

The Uranium atom U23892 decays by particle emission

U238

92He

4

2+ ?

234

90

What is represented by ?



More decay reactions

The Thorium atom Th22790 decays by particle emission

Th227

90

Complete the equation




Th227

90He

4

2+ Ra

223

88




The Actinium atom Ac22589 decays by 3 particle emissions

Ac225

89

Complete the equation




Ac225

893He

4

2+ Bi

213

83



Particle emissions

Particles are electrons but they do not come from the electron

shells which surround the nucleus – they come from the

nucleus itself.

The electron is emitted when a neutron becomes a proton.

N10 p1

1 0-1



Particle emissions

The effect of Particle emission is to increase the proton count

by 1 whilst leaving the overall mass unchanged.

Th231

90

0

-1+ ?

What is ?



Particle emissions

The effect of Particle emission is to increase the proton count

by 1 whilst leaving the overall mass unchanged.

Th231

90

0

-1+ Pa

Notice how particle emission raises the atomic number by 1

231

91



Decay Series

When a radioactive nucleus such as U23892 decays it

often produces another radioactive isotope which

goes on to decay further.

We are going to construct a decay series on

graph paper for the element U238

92 to show howit eventually forms a stable isotope of lead

Pb20682



GET A PIECE OF GRAPH

PAPER• Draw a vertical axis representing atomic

mass. It will need to run from 200 to 240

• Draw a horizontal axis representing atomicnumber. It will need to run from 78 to 93.

• Position the isotope U23892 on your graph

and mark it clearly.



240

20078 93

Mass

Number

* U23892



Plotting an decay

• The nucleus gives off an alpha particle first

to form a new nucleus

• Work out what the new nucleus is

• Find the nucleus on your graph and add it in

• Join the points with an arrow



240

20078 93

Mass

Number

* U23892

Th23490 *



Plotting a beta emission

• The Thorium next loses a Beta particle

• Work out what would be formed

• Add the nucleus onto your chart



240

20078 93

Mass

Number

* U23892

Th23490 * * Pa234

91



Building up the decay series

Continue to build up the series using the following

emissions. Each alpha emission is shown as a

diagonal to the left and each beta emission is ahorizontal line to the right.

If you are successful you should end up with Pb20682

Good Luck !



Emission sequence (including the

first two example emissions)

1.

2.

3.

4.

5. 6.

7.

8.

9.

10.

11.

12. 13.

14.

ci2.2 nuclear reactions

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