P2.5 Flashcards
What makes each element unique
It’s atomic number or proton number. The number of protons it has
What is the mass or nucléon number
The number of sub atomic particles in the nucleus of an atom. Protons + neutrons
What are isotopes
Same element but different nucléon number. Same protons but different number of neutrons
What is ionising radiation
Radiation with enough energy to remove electrons from atoms, causing them to become ions
What is a radioactive substance and what do they do
Substances with an unstable nucleus. They become more stable by decaying, giving of energy
What is an alpha particle and properties
They are decay particles with 2 protons and 2 neutrons. They are emitted very fast and are heavy. They are very ionising as they are so big and each time they ionise, they lose energy. They ionise lots of atoms fast so lose energy quickly so aren’t very penetrative. They’re stopped by paper
Properties of b- particle
Electron emitted from an unstable nucleus when a neutron becomes a proton. Much less ionising than alpha so they can penetrate further. They are stoped by few mms of aluminium and even thinner lead
Properties of gamma rays
High frequency electromagnetic waves and about ten times less ionising than beta particles. They can travel severe kms in air and are stopped by very thick lead. Most penetrating but least ionising
What kind of energy do alpha particles, beta particles and gamma rays have
Alpha and beta have kinetic and gamma have electro magnetic
What happens in fission
An unstable nucleus absorbs a neutron. This causes it two split into two daughter, smaller nepuclei and 2 or more neutrons as well as lots of energy, thermal and kinetic. These neutrons may then collide and be absorbed by other unstable nucleuses so the chain reaction continues
What happens in the fission of uranium 235
Splits into krypton 92 and barium-141 as well as 3 neutrons, thermal and kinetic energy
What happens in atomic bonds
Fission occurs in an uncontrolled chain reaction so the energy is quickly released into the environment
What is the fuel for nuclear power stations and how is it made
It’s mostly uranium and a little plutonium. They are made into little pellets which are then put into fuel rods. These rods are then put into the reactor core
How are nuclear reactors controlled
To stop them exploding, the neutrons emitted have to be absorbed by something so only one neutron from each atom will cause another fission. This keeps the reactions at a constant rate. To do this, neutron absorbing materials are put into control rods which are placed between fuel rods in the reactor core. These can be raised and lowered in order to absorb more or less neutron to regulate the amount of reactions. To shut it down, the control rods are lowered fully to absorb all free neutrons
What is a moderator for
For fission to occur, the neutron has to be absorbed into the unstable nucleus. In fission, the neutrons are emitted very fast so in reactors, the neutrons have to be slowed down so they are more likely to be absorbed. The moderator slows down the neutrons
