3.4 - Nuclear Reactions

Question 0

What is a ‘radionuclide’?

Answer 0

It is an isotope that decays radioactively

Question 1

Describe Geiger and Marsden’s experiment (1) and explain what Rutherford’s conclusions of this experiment were (2)

Answer 1

A stream of alpha particles was fired at a thin sheet of gold foil in a vacuum. Most particles passed straight through, a few were deflected through large angles and 1 in 8000 came backwards
• This suggested that most of the atom must be empty space, as many particles passed through
• This also suggested that most of the mass and positive charge of an atom is concentrated in a very small volume (in the nucleus), as some particles were deflected or bounced back

Question 2

What is an ‘isotope’?

Answer 2

These are nuclides of an element that have the same atomic number but a different mass number

Question 3

What is meant by alpha emission/decay? (2)

Answer 3

• An alpha particle has two protons and two neutrons
• The emission of an alpha particle from a nucleus must form a daughter with an atomic number decreased by 2 and a mass number decreased by 4

Question 4

What is meant by beta emission/decay? (2)

Answer 4

• In a beta decay a neutron in the nucleus changes into a proton and an electron
• The daughter product has the same mass number but the atomic number increases by 1

Question 5

What is meant by gamma emission/decay? (1)

Answer 5

This is the high frequency radiation releases when there are changes in the internal structure of a nuclei

Question 6

What is Nuclear Fission?

Answer 6

In fission, a nucleus with a large mass number splits into two nuclei of smaller mass numbers, usually with the release of neutrons and thus energy is also released.

Question 7

What is ‘Spontaneous’ Fission?

Answer 7

This means that each fission occurs at random, nut the half life will be constant for a large number of atoms

Question 8

What is ‘Induced’ Fission?

Answer 8

This is when fissions are induced by neutron bombardment, and the incident neutron can stimulate the fission of a nucleus with a large mass number

Question 9

What is Nuclear Fusion?

Answer 9

This is when two nuclei combine to form a nucleus of larger mass number, and a large amount of energy is released.

Question 10

Explain how the products of fission and fusion acquire large amounts of kinetic energy

Answer 10

• The mass of the products is always less than the mass of the starting materials, and this missing mass is called the lost mass
• The mass and energy and equivalent, so the lost mass is turned into released energy using E = mc^2