Physical Science: Nucleosynthesis and Origin of Elements - PDF

SECOND SEMESTER PHYSICAL SCIENCE SUBJECT TEACHER: Ms. Joanalyn D. Basilides  CONTENTS OF THE SUBJECT Formation of Elements in the Big Bang and Stellar Evolution Elements and Isotopes The Emergence of Ideas about the Atom The Development of the...

SECOND SEMESTER PHYSICAL SCIENCE SUBJECT TEACHER: Ms. Joanalyn D. Basilides  CONTENTS OF THE SUBJECT Formation of Elements in the Big Bang and Stellar Evolution Elements and Isotopes The Emergence of Ideas about the Atom The Development of the Atomic Structure Polarity and Intermolecular Forces of Attraction Chemistry in Everyday Lives Biological Molecules Chemical Reactions CONTENTS OF THE SUBJECT Early Models of the Universe The Restless Universe Aristotle vs. Galileo Newton’s Laws in Pulley Systems Energy in Motion Introduction to Light Waves Photon Theory of Light Wave Theory of Light Formation of Light and Heavy Elements The Origin of Light Elements The origin of all 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. Nucleosynthesis is the process that creates new atomic nucleus from preexisting nucleons, which is proton neutrons. Primordial or Big Bang Nucleosynthesis refers to the process of producing the “light elements” shortly after the Big Bang. The energy and temperature of the universe are extremely high to cause the neutrons and protons to combine and form certain species of atomic nuclei in a process called nuclear fusion. Proton Neutron s s 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. An Isotope is a form of an element that has the same atomic number of the original element but with different atomic mass or mass number. Origin of Heavier Elements Heavy elements were formed only billions of years after the formation of stars. The density inside a star is great enough to sustain fusion for extended time periods required to synthesize heavy elements. 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”. There are many nuclear synthetic pathways or nuclear fusions to produce heavy elements: Carbon-Nitrogen-oxygen cycle Proton-proton fusion Triple alpha process Layers near core of stars have very high temperatures enough to nucleosynthesize heavy elements such as silicon and iron. Elements heavier than Iron 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. The density inside a star is great enough to sustain fusion for extended time periods required to synthesize heavy elements. A supernova is the explosive death of a star In supernova, neutron capture 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. Adding neutrons to a 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 supernova.