hello grade 11 welcome in our previous video you learned that light elements hydrogen helium lithium and beryllium are the only elements formed in the early universe through the process called big bang nucleosynthesis the continuous expansion of the universe decreases the temperature which is needed for collisions of particles through coordinate universe elements and protons the question now is how do the heavier elements form after the big bang sengali elements today you will learn how the elements heavier than beryllium are formed during the evolution of the star through the process called stellar nuclear synthesis at the end of this video you should be able to explain how the heavier elements are formed during star formation and evolution formation of heavier elements started million years after the explosion that is the time when a vast cloud of gas and dust called nebula start to collapse due to the action of gravity in a geologic blink of an eye a hundred thousand years gravity pulled the clouds together creating a protostar in the center where molecules crush together pressure and temperature rise up incredibly the newborn star becomes hot enough for nuclear fusion to occur starting the process called stellar nucleosynthesis standard nucleosynthesis is the process by which elements are formed within the stars as a result of nuclear fusion nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus since the stars are composed primarily of hydrogen the first fusion process occurs in the hydrogen core of the stars such as the sun with a temperature of less than 15 million kelvin in the process known as the main branch proton proton chain deuteron an isotope of hydrogen if you can recall in our previous video forms helium 3 when fused with a proton this is known as the diotherium burning this immediately consumes all the diuteron produced in the early universe then helium-4 forms from helium-3 fusion as you can see when helium-3 combines with another helium-3 the reaction produces a helium-4 and two protons this nuclear fusion releases tremendous amount of light heat and radioactive energy represented by this symbol the gamma ray and it a result on a nuclear tissue non-hydrogen para magic is angelio nasagnitum state and arrow nating since helium is heavier than hydrogen and as more and more hydrogen is burned into helium the core of a star becomes comprised of helium as hydrogen is depleted the star now have a very dense helium core and a hydrogen shell due to this process the temperature and density of the core of the star increases up to 100 million kelvin the star's thermal pressure causes it to push out the gas and the star balloons into a red giant because of the increase in temperature several nuclear fusion processes will occur in red giant aside from hydrogen fusion the first is the triple alpha process alpha particles refer to helium-4 this reaction involves diffusion of three helium-4 atoms in the following steps two helium-4 atoms will react to form beryllium eight and then the beryllium eight produced reacts with another helium four to form carbon 12. the second one is the carbon fusion cycle or the cno cycle a process where carbon-12 is used as a catalyst that facilitates the production of helium once it was already present from the alpha processes sienna cycle is the process that involves repeated proton capture and beta plus decay to give you a short review parameters may be listed in my tilde and associated with the chemical reactions this nuclear symbol for example helium h e represents the symbol of the element this number sata represents the number of protons and neutron in the nucleus we call it the mass number and this one represents the number of protons and we call this one the atomic number remember that each element has a unique number of protons and the periodic table was arranged according to increasing number of protons heavier elements of us heavier elements than now going back let's continue alpha fusion processes continue in the core via the alpha ladder more and more alpha particles are fused to create heavier elements all the way to iron making the core and the start itself more as if yes i say nothing the carbon 12 produce in the triple alpha process will also react with helium producing the element oxygen now looking at the reaction the mass number of carbon 12 plus helium 4 is 16. and now the atomic number or the number of proton is 6 plus 2 is eight to determine what element is formed in the reaction we simply consider the atomic number therefore the number eight in the periodic table is oxygen that simple the alpha ladder continues oxygen reacts with helium atomic number eight plus two is ten what element is number ten in the periodic table correct neon how about this one yes magnesium alpha fusion continue in the core via the alpha ladder the other particles create heavier elements all the way to iron making the core of the star amana bone elements a star a hangang iron lamp elements heavier than iron like copper known as a wire gold and gold necklace thin and silver the star keep growing as it accumulates mass up to the point where the star will eventually be unable to generate energy to push against gravity due to the formation of heavier elements thus causing it to collapse on itself it then undergoes planetary nebula for a medium-sized star like our sun or supernova for massive stars now supernova releases tremendous amount of energy enough to synthesize elements heavier than ions therefore hindi asylum boss and obtain star they were formed during supernova exclusion among elements heavier than iron this is done through the r process that involves rapid capture of neutrons by the atom other heavy elements are also synthesized through s-process involving slow neutron capture in red giants after the explosion the stars like ours will become a white dwarf and later on becomes a black dwarf like a stone lost in space for massive sparse neman either they become a neutron star or a black hole and that's all for today shout outs among teachers come very supportive please subscribe to his channel bernard gomez for instructional videos and mathematics thank you all for watching [Music]