Nuclear Fission (Edexcel GCSE Physics)

• Nuclear fission is defined as:

The splitting of a large, unstable nucleus into two smaller nuclei

• Isotopes of uranium and plutonium both undergo fission and are used as fuels in nuclear power stations
• During fission, when a neutron collides with an unstable nucleus (the parent nucleus), the nucleus splits into two smaller nuclei (the daughter nuclei) as well as two or three neutrons
  • Gamma rays are also emitted

A uranium-235 nucleus is struck by a neutron, breaking it into two smaller daughter nuclei and 2 or 3 neutrons

• These products of the fission reaction move away very quickly
  • Energy is transferred from the nuclear store to the kinetic store of the products
  • Eventually this energy can be used to heat water to produce steam to generate electricity within the nuclear power station

ANSWER:  D

Step 1: Identify the different mass and atomic numbers

• • Pu (Plutonium) has mass number 239 and atomic number 94
  • Pd (Palladium) has mass number 112 and atomic number 46
  • Cd (Cadmium) has mass number 124 and atomic number 48

Step 2: Calculate the mass and atomic number of the missing section

• • Mass number is equal to the difference between the mass numbers of the reactants and the products

239 – (112 + 124) = 3

• • Atomic number is equal to the difference between the atomic numbers of the reactants and the products

94 – (46 + 48) = 0

• • The answer is therefore not B or C

Step 3: Determine the correct notation

• • Neutrons have a mass number of 1
  • The answer is therefore not A
  • Therefore, this must be three neutrons, which corresponds to D