Mass defect and nuclear binding energy (23.1)

What is the relationship between mass and energy?

E = mc²

Where E is energy (J)

Where m is mass (kg)

Where c is the speed of light (ms^-1)

What does the relationship between mass and energy show?

It shows that mass can be converted into energy and vice versa.

e.g. if a particle is travelling fast enough it will gain mass

What is the AZX notation for atomic nuclei?

Where A the number of protons and neutrons

Where Z is the number of protons

Where X is the symbol of the element

In nuclear reactions, A and Z are conserved

What is meant by mass defect?

Mass defect - the difference between the mass of a nucleus and the total mass of the nucleons when separated to infinity

The mass of the nucleus is always lower than the total mass of its nucleons

Why is the mass of a nucleus smaller than the mass of the individual nucleons that make it up?

When a nucleus is formed energy is released. Since E = mc² and energy is released, mass decreases.

What is binding energy and the energy associated with it?

Binding energy - the minimum energy required to completely separate the nucleons in a nucleus to infinity

E_b = Δmc²

Where E_b is binding energy (J)

Where Δm is the mass defect (kg)

Where c is the speed of light (ms^-1)

What makes a nuclear reaction energetically possible?

For a nuclear reaction o be energetically possible, the total binding energy of the products must be greater than the total binding energy of the reactants

What does the graph of binding energy per nucleon against nucleon number look like?

The greater the binding energy per nucleon, the more stable the nucleus

What is nuclear fusion and under what conditions does it occur?

Nuclear fusion - the fusing together of two lighter nuclei to form a heavier nucleus

Fission only occurs in high energy environments as it takes a lot of energy to overcome the electrostatic repulsion from the nuclei repelling each other

What is nuclear fission and how is it induced?

Nuclear fission - the splitting of a large nucleus into smaller nuclei

Nuclear fission is induced by firing neutrons at a large nucleus. When the nucleus absorbs a neutron it splits into smaller nuclei. During fission, neutrons are emitted which go on to be absorbed by other large nuclei, causing a chain reaction

How can the energy produced in nuclear reactions be calculated?

E = Δmc²

Where E is the energy released in the reaction (J)
Where Δm is the mass difference between the products and reactants (kg)

Where c is the speed of light (ms^-1)

What are the energy transfers in fission and fusion?

In fission the potential energy due to the strong nuclear force is released when the lighter

nuclei are joined together.

In fusion electric potential energy of the electromagnetic force is released when the positively charged nuclei move apart