2 - extra

Question 1

What are nucleons?

Answer 1

The main constituents of atomic nuclei - protons and neutrons

Question 2

What is binding energy?

Answer 2

Protons within the nucleus repel each other, and so energy is required to hold nucleons together in the nucleus. This energy is called binding energy.

Question 3

What is meant by the term ‘mass defect’?

Answer 3

The mass of an atom has a mass lower than expected from adding the masses of the protons and neutrons. This mass defect is accounted for by the binding energy (mass and energy are related, as shown by the equation E=mc^2)

Question 4

How does binding energy vary with mass number?

Answer 4

Elements with lower and higher mass numbers have a lower binding energy per nucleon, and are therefore less stable.

Elements in the middle of the periodic table, such as iron, have a higher binding energy per nucleon.

Question 5

How is the mass defect utilised in nuclear fission?

Answer 5

In fission, a larger nucleus is converted to a more stable nucleus. The loss in mass, the mass defect, is equal to the binding energy, which is the energy that is released.

Question 6

How is the mass defect utilised in nuclear fusion?

Answer 6

In fusion, a smaller nucleus is converted to a more stable nucleus. When combining the nuclei, there is a loss in total mass, the mass defect. This is equal to the binding energy, which is the energy that is released.

Question 7

Break down the steps required to calculate mass defect when given a nuclear equation.

Answer 7

1. Check that the atomic numbers and mass numbers are balanced in the reaction.
2. Calculate the total mass before the reaction
3. Calculate the total mass after the reaction
4. Calculate the difference between these masses (mass defect)
5. Using E=mc^2, calculate the energy released