Physics P2

Nuclear Fission:

Nuclear Fission occurs when a stable ISOTOPE is hit by a neutron. The Isotope absorbs neutron, becomes unstable and splits apart. THIS DOESNT HAPPEN NATRUALLY.

2 Examples, both used in nuclear power stations and nuclear bombs:-

Uranium-235

plutonium-239

E.G.

Uranium-235 + Neutron --> Fission (Uranium-235) -->Strontium-90 +Xenon-144+Neutrons

This is a CHAIN REACTION. Which means the neutrons would be absorbed by the strontium and xenon and this would carry on.

If this reaction is uncontrolled too much energy realeased and causing steam explosion, sending radioactive material into the atmosphere, e.g. Chernobyl, Ukraine

The energy realeased from the fission of 1KG of Uranium is more than burning 2 Million tonnes of Coal.

Nuclear Fusion is the power that fuels the sun and all the stars. Small nuclei join together to form a larger nuclei and energy is realeased. This takes very high pressures and temperatures, to overcome the repulsive force (both nuclei are positive) and force them together. There are enormous technical difficulties with this method of releasing energy.

Deuterium-2 + Tritium-3 -->Fusion--> Helium-4 + Neutron

This shows 1 way the fusion reaction could work, notice the total number of atoms is the same, they are just arranged differently.

THIS OCCURS NATRUALLY.

Nuclear Fission:

• Uses Uranium Isotope
• Highly Radioactive Products
• Produces Nuclear Weapons Material
• Control Rods Needed For Safety

Nuclear Fusion

• Uses Hydrogen Isotopes
• No Radioactive Products
• Process Which Happens In The Sun
• Technically Very Difficult

Ions - Charged atoms, as a result of an unequal number of electrons an protons Isotopes - Atoms of the same element with different number of neutrons There are 3 ways for a unstable nucleus to become more stable. These are; Alpha Decay, Beta Decay and Gamma Decay

• Type of Decay: Alpha Decay
• Change In Nucleus: Loses 2 Protons and 2 Neutrons
  
• Particle Emitted: 2 Protons and 2 Neutrons as a Alpha Particle (Same As A Helium Nuclei)
  
• Charge : Positive
  
• Properties: Slow and Heavy

• Type of Decay: Beta Decay
  
• Change In Nucleus: A Neutron In The Nucleus changes into a Proton
  
• Particle Emitted: An Proton and Electron are created in the Nucleus and the Electon is instantly Emitted
  
• Charge : Negative
  
• Properties: Fast and Light

Gamma Radiation is emmitted by some ustable nucleui. Gamma radiation is uncharged andhas no mass, so the nucleus does not change. It is part of the electromagnetic spectrum and is emitted in waves

What we think of as the structure of the atom was discovered by Ernst Rutherford and 2 of his students. They fired a stream of alpha particles at a think layer of gold atoms. They found that most of the particles went straight through the gold, but some were reflected. We now know, that this is because, most atoms is empty space with a positive nucleus and a few electrons moving around it. This was a complete surprise to Rutherford, because previously to this scientists had used Thompson's Plum Pudding model of an atom which had a positive atom with electrons dotted threought out it. This should have meant that the stream of alpha particles were always reflected.

This is a good example of scientists reviewing ideas based on the results of their practices.