1. Nuclear Reactions

2. The ABC of Radiation
An unstable nucleus (radioisotope) attempts to become stable by emitting matter… (A is for ATOM)
Historically, the products of radioactivity were called alpha, beta, and gamma when it was found that they could be analyzed into three distinct types by an electric field.

3. The Alpha particle: a
Composed of two protons and two neutrons, the alpha particle is a nucleus of the element helium.
It has a charge of 2+
and the symbol… or

4. The Beta particle: b
Is a fast moving electron which comes from the nucleus of the decaying atom.
It has a charge of 1-
and the symbol…

5. g The Gamma ray: g It has no mass, no charge,
Is an electromagnetic wave emitted. It does not affect the number of protons or neutrons in the nucleus
and the symbol
Gamma Ray
If an alpha or beta emission takes place, it is usually accompanied by a gamma ray.

6. Absorption of alpha, a, beta, b, and gamma, g
Few cm of air or thin paper
Few mm of aluminium
Few cm of lead
Alpha radiation causes the greatest ‘ionisation density’

7. Decay Series
When an unstable parent nucleus decays, the daughter product which is formed may also be unstable. This will decay in turn, in a decay series. eg
*The total mass and atomic no. are always conserved*
Parent Daughter Alpha
then
*Gamma emission do not affect Z or A*

8. Other decay products
In a decay series, individual neutrons and protons may also be produced. These can be shown in a similar way:

9. Nuclear Fission
Occurs when a heavy unstable nucleus splits, producing two lighter nuclei, along with neutrons and a release of energy.
Fission can occur spontaneously, or be caused by neutron bombardment

10. E = mc2
Although the mass number is conserved, (showing that all protons and neutrons are accounted for), accurate measurements show that a very small mass has been ‘lost’ during the reaction.
Einstein explained that mass is just another form of energy.
The very small mass has been converted into energy...released as:
heat energy, and
kinetic energy (gained by the fission products)
The energy released equals the mass lost times the speed of light2
ie E = mc2

11. Nuclear Fusion
Occurs when two light nuclei combine, producing one nucleus of larger mass number, again with a release of energy.

12. Calculations
In the fusion reaction shown, calculate the energy released.

13. Calculations Mass before reaction (LHS) Mass after reaction (RHS)
Mass lost:= LHS-RHS
Energy released: