Lesson 1 | Formation Of Elements

• The widely accepted explanation for the origin of the universe is the Big Bang theory
• The Big Bang model is a description or a model of the very early universe, not a theory of the origin of the universe
• The process of producing "primordial elements" Hydrogen, Helium, and Lithium shortly after the Big Bang is known as Big Bang Nucleosynthesis
• High temperature is needed to fuse protons and neutrons to form nuclei in nucleosynthesis
• An isotope is an atom of an element with the same number of protons but a different number of neutrons
• Stellar formation and evolution inside stars is how heavy elements formed after the Big Bang
• As the universe continued to expand, stars made of Hydrogen became hotter and denser
• Energy from nuclear fusion reactions between light elements releases high amounts of energy in stars
• If the energy or fuel is depleted in stars:

  • Small Stars convert Hydrogen to Helium
  • Medium Stars convert Helium to Carbon and Oxygen
  • Massive Stars convert Helium to Hydrogen and Carbon
• Protons can be combined with neutrons to form heavier elements in a process called nuclear fusion
• The CNO cycle is a process in which the average star gets energy and converts Hydrogen to Helium
• The Alpha ladder process converts Helium into heavier elements
• As stars age, they undergo supernova to form elements heavier than Iron as the basis for matter
• Elements produced from supernova cannot be produced by nuclear fusion but through the capture of neutrons or if an electron is emitted and the nucleus becomes a heavier isotope of the element
• The S-process or slow process involves the slow addition of neutrons that may produce stable isotopes up to Lead (Pb) and can happen inside a star before it explodes
• Beta decay occurs when, in a nucleus with too many protons or neutrons, one of the protons or neutrons is transformed into the other, changing a proton into a neutron and allowing the two particles to combine
• The R-process or rapid process involves neutron capture that occurs very fast and turns into a heavier nucleus before beta decay
• Neutron capture and beta decay are processes involved in forming elements heavier than Iron
• Proton-proton Chain Reaction

  • A process which the average star gets their energy and converts H to He.
• CNO Cycle

  • helium as its end product.
  • it starts with carbon and acts as a catalyst for the reaction.
  • it produces energy in main sequence stars.

  the main part of the cycle involves C and N, while the ON cycle usually contributes little energy.
• this chain of Alpha Process is also termed the alpha ladder.
• in this, an alpha particle is added to an atomic nucleus (such as carbon) to form oxygen.
• the addition of an alpha particle to an atom adds 2 protons (and therefore the atomic number of the product is 2 is larger than the original).
• Silicon Burning: Photo-Disintegration-Rearrangement
• Elements are known to have been formed during...

  • big bang nucleosynthesis (H, He, Li)
  • stellar formation & evolution (Be to Fe)
  • stellar explosion (Elements heavier than Fe)