Nuclear Force and Particles Principles of Physics

Models of the Atom Understanding of wave-particle duality led to better understanding of the atom It was determined that the protons and neutrons occur together in the center with electrons orbiting it at various locations But, how does the nucleus stay together when it is made up of like and neutral charges???

Nuclear Forces Strong Force: – attractive force between particles in nucleus Keeps nucleus stable 100 x stronger than the electrostatic force only effective at small distances (short range) breaking “bonds” – releases a lot of energy

Nuclear Force Weak force: responsible for the radioactive decay Weaker than strong and electromagnetic forces For large atoms the strong force is not always strong enough to hold the nucleus together The weak force breaks the atom into smaller more stable atoms while releasing energy The weak force is responsible for such things as the sun being able to produce energy and carbon dating

Einstein’s Mass-Energy Equation Mass is another form of energy. To find the mass equivalent of energy we use Einstein’s famous equation:   E=mc2    E = energy (J) m = mass (kg) c = speed of light in a vacuum = 300,000,000 m/s

Mass-Energy Conversions Example: Energy from the sun is produced through radioactive decay. The sun’s mass is being converted into energy. As the Sun’s energy comes to Earth , it’s mass will continue to decrease. Example: During chemical reactions when atoms combine the sum of the mass of the individual atoms before the reaction is not equal to the mass of the combined atoms after the reaction. The excess mass was converted to energy.

Fission Fission: splitting of large atoms resulting in the release of energy The energy released is related to the mass lost through E= mc2 Fission can occur as a chain reaction Atomic bomb Nuclear reactors

Fusion Fusion: Combining of small atoms to make larger ones and a release of energy The energy released is related to the mass lost through E= mc2 Fusion requires a huge amount of energy to activate The sun and stars produce energy through fusion No successful fusion reactors exist on Earth, because of the conditions necessary to activate the reaction

Elementary Particles Although it was believed for a very long time that protons, neutrons, and electrons were the smallest particles, they were wrong… Types of particles 1. Baryons (include protons and neutrons) Made up of three smaller particles called quarks 2. Mesons Made up of two quarks 3. Leptons (include electrons and neutrinos) 4. Bosons

Antimatter Antimatter: Matter that has all the same properties as the regular matter except the electric charge is reversed Example: positron (anti-electron), has the same mass as an electron, but is positively charged Antimatter does not occur in the natural universe as far as we know. It can be created in labs in very small quantities.

Matter – Antimatter Interactions When a particle and an antiparticle meet, both are turned into pure energy   Matter – antimatter reactions are the most energetic reactions in the known universe Example: If 500 kg of water were added to 500 kg of anti-water, the energy released would be able to power the entire US for a year!!