Atoms and Nuclei

Atoms and Nuclei

1. Inside the atom

   • nucleon
     • proton
     • neutron
   • structure
     • positively charged nucleus composed of protons and neutrons
     • electrons that surround the nucelus
   • Charge
     • electron
       • relative charge = -1
       • charge (C) = -1.60x10-19
     • proton
       • relative charge = +1
       • charge (C) = +1.60x10-19
   • mass
     • proton
       • relative mass = 1
       • mass (kg) = 1.67x10-27
     • neutron
       • relative mass = 1
       • mass (kg) = 1.67x10-27
     • electron
       • relative mass = 1/2000
       • mass (kg) = 9.11x10-31

2. Isotopes

   • Isotopes are atoms with the same number of protons and electrons
   • different number of neutrons

3. Specific Charge

   • its charge divided by its mass (Ckg-1)

4. Stable and Unstable Nuclei

   • strong nuclear force
     • attractive range from 0.5fm to 4fm
     • same effect between all nucleons
       • proton-proton
       • proton-neutron
       • neutron-neutron
   • beta radiation (β)
     • emission of an electron from the nucleus
     • when a β particle is ejected, neutron turns into a proton
     • happens in isotopes that are 'neutron-rich'
     • an antineutrino is also released
   • alpha radiation (α)
     • 4 nucleons
     • 2 protons
     • only happens in very big nuclei
     • too big for the strong nuclear force to keep stable
   • gamma radiation (γ)
     • nucleus has too much energy
       • usually after alpha or beta decay

5. Particles

   • Particles and Antiparticles
     • they have equal mass and if charged, the equal but opposite charge
     • when energy is converted into mass, there are equal amounts of matter and antimatter
     • pair production
       • a gamma ray photon with enough energy will produce mass
         • usually electron-positron because of their low mass
       • usually happens near the nucleus because it conserves momentum
     • annihilation
       • particle and antiparticle meet they annihilate
         • all of their mass gets converted back into energy

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