Download to read offline
More Related Content
PS-mod
- 1.
- 2. THE FORMATION OFTHE ELEMENTS DURING THE BIGBANG AND STELLAR EVOLUTION
- 3. The origin ofall the naturally occurring elements fall into two phases: •Big Bang or Primordial Nucleosynthesis —the origin of the “light” elements; and • Stellar Nucleosynthesis— the origin and production of the “heavy” elements. The Origin of Light Elements
- 6. Through Nuclear Fusion,the light elements- Hydrogen (H), Helium (He), and small amounts of lithium (Li) and beryllium (Be) were formed. The isotopes produced during the big bang nucleosynthesis were H-1, H-2, H-3, H-4, L-7.
- 7. An isotope isa form of an element that has the same atomic number of the original element but with different atomic mass or mass number.
- 8. Origin of HeavierElements Heavy elements were formed only billions of years after the formation of stars. Created when pairs of neutron stars collide cataclysmically and explode The density inside a star is great enough to sustain fusion for extended time periods required to synthesize heavy elements.
- 9. Origin of HeavierElements Stars are hot and dense enough to burn hydrogen-1 (1H) to helium-4 (4He). The formation of heavy elements by fusion of lighter nuclei in the interior of stars is called “stellar nucleosynthesis”.
- 10. Origin of HeavierElements There are many nuclear synthetic pathways or nuclear fusions to produce heavy elements: •Carbon-Nitrogen-oxygen cycle •Proton-proton fusion •Triple alpha process
- 11. Origin of HeavierElements Layers near core of stars have very high temperatures enough to nucleosynthesize heavy elements such as silicon and iron.
- 12. Elements heavier thanIron Elements heavier than iron cannot be formed through fusion as tremendous amounts of energy are needed for the reaction to occur. Heavy elements are formed in a supernova, a massive explosion of a star.
- 13. A supernova is theexplosive death of a star
- 14. In supernova, neutroncapture reaction takes place, leading to formation of heavy elements. In a neutron capture reaction, heavy elements are created by addition of more neutrons to existing nuclei instead of fusion of light nuclei.
- 15. Adding neutrons toa nucleus doesn’t change an element. Rather, a more massive isotope of the same element is produced. Elements higher than iron requires tremendous amount of energy to be formed. Thus, they were produced from a neutron capture reaction in a
- 16. Summary: There are 3reactions that led to the formation of the elements: nucleusynthesis, fusion, and neutron capture reaction. These reaction required a certain amount of energy to proceed, which was obtained from the heat of the continuously expanding universe. Thus energy in the form of heat does not only produce work but also the elements that make up matter that we have today. The reaction involved in the formation of these elements are dependent on the atomic mass of the elements. More energy, and thus higher temperature, is needed to form heavier elements. Nucleuosynthesis formed light elements, whereas fusion in stars formed elements with an atomic mass that is within the range of beryllium and iron. Thus any element with an atomic mass higher than iron, which required tremendous amount of energy to be formed was produced from a neutron capture -reaction in supernova.
- 17.