Ionising Radiation and Nuclear Reactions.

Question 1

Nuclear Model of the Atom

Answer 1

The atom is composed of a nucleus containing protons and neutrons, which are kept together through the strong nuclear force. Electrons occupy orbitals around the nucleus and are kept there because of electrostatic attractions.

Question 2

Why do protons in the nucleus repel each other?

Answer 2

Protons repel each other because they have the same charge, thereby electrostatically repulsing one another.

Question 3

Define the Strong Nuclear Force

Answer 3

The Strong Nuclear force is one of the four fundamental forces. It acts over small distances in the nucleus of an atom to overcome the electrostatic repulsion forces between protons.

Question 4

What makes a nucleus stable?

Answer 4

• The greater the binding energy per nucleon, the more stable an atom is
• Neutrons act as the carriers of the strong nuclear force and act as the ‘glue’ of the nucleus
• As the number of protons increases, so must the number of neutrons to overcome the repulsive forces.

Question 5

Explain natural radioactive decay in terms of stability.

Answer 5

The process by which atoms lose mass and energy to reach a more stable state. Instability can arise if an atom has too much energy or there is an imbalance of particles which imbalances natural forces.

Question 6

Alpha radiation

Answer 6

Radiation whereby a helium nucleus is ejected from an atom.

• Low penetrating power
• Large mass
• High ionisation ability over short distances
• Charge of 2+

Question 7

Beta positive radiation

Answer 7

Radiation where a positron is ejected from a nucleus.

• High speed, high energy
• Can travel further than alpha particles
• Charge of +1

Question 8

Beta negative radiation

Answer 8

Radiation whereby an electron is ejected from a nucleus

• High speed, high energy
• Can travel further than alpha particles
• Charge of -1

Question 9

Gamma radiation

Answer 9

The radiation where an electromagnetic gamma-ray is emitted from a nucleus to

• Highest energy, highest penetrating ability
• They don’t cause as much damage

Question 10

Alpha Decay

Answer 10

• Too much mass
• Strong nuclear force cannot compensate for the large molecule and the electrostatic forces between protons.
• Excited daughter nucleus releases energy

Question 11

Beta Positive decay

Answer 11

• Proton decays into a neutron and a positron.
• Too many protons
• Daughter has a -1 proton

*an Isolated proton will not decay into a neutron and a positron.

Question 12

Beta negative decay

Answer 12

• Too many neutrons
• Nucleus emits an electron and an antineutrino
• A neutron decays into a proton

Question 13

Gamma Decay

Answer 13

• Too much energy

- Atoms emit an electromagnetic wave to ascend to a lower energy level

Question 14

Explain how through multiple decays a nucleus will become stable.

Answer 14

To reach the most stable nucleus, an atom will undergo a series of radioactive decay step too loose either mass or energy that is causing the particle to be unstable. This is called a decay series

Question 15

Half-Life

Answer 15

Half-life is the time taken for a sample of atoms of a particular element to decay and leave half of the remaining atoms.

Question 16

Describe Energy in terms of electron volts and joules

Answer 16

When energy is explained in terms of electron volts, we mean the amount of energy required to move an electron across a potential difference of 1V. When talking about energy in joules, we are referring to the amount of work needed to move a force over a distance.

Question 17

Define artificial transmutation

Answer 17

Transmutation that is initiated by artificially bombarding a nucleus with particles to make it unstable and then decay.

Question 18

Distinguish between natural and artificial radioactive decay.

Answer 18

Natural transmutation occurs when particles naturally lose mass or energy to achieve a more stable state, through Alpha, Beta and Gamma Decay. However artificial transmutation can occur when an atom is stable but is forced into decay because it is bombarded with particles

Question 19

Nuclear Fission

Answer 19

A process by which an artificially induced unstable nuclei splits into two smaller nuclei, releasing neutrons and energy.

Question 20

Explain a neutron-induced fission reaction

Answer 20

occurs when neutrons bombard a nucleus, causing it to become unstable and wobble, (according to the water-drop model for fission), and split, becoming two smaller nuclei, some neutrons and energy.

Question 21

Explain a fission chain reaction

Answer 21

A chain reaction occurs when the products of one reaction are the reactants of another, similar reaction. This produces a cascade of reactions.

• A neutron-induced fission chain reaction is propagated by the fact that neutrons are the initiators of the chain reaction, and are released by the reaction.

Question 22

Nuclear fusion

Answer 22

The process whereby two lighter nuclei bind to become a heavier nucleus and release some small subatomic particles.

Question 23

Mass Defect

Answer 23

The discrepancy between the mass of the constituent particles and the mass of the nucleus of those particles.

Question 24

Binding energy

Answer 24

The work that must be done to prevent nuclides from breaking apart. It is the mass defect.

Question 25

Binding energy per nucleon.

Answer 25

The amount of binding energy between particles of an atom.

Question 26

Einsteins Mass-Energy Equivalence relationship.

Answer 26

DeltaE = Delta M C^2

Where delta E is the change in energy and delta M is the mass defect in kilograms.

Question 27

Determine which type of artificial transmutation releases the most energy?

Answer 27

Fusion outputs 7 times the energy as fission. Because the Fission nucleus is large, the energy per kilogram values is smaller than the fusion output. Therefore, the fusion reaction produces more energy per unit mass due to their size, and more mass is transformed into energy.