The Origin of Chemical Elements
Astronomers believe that the universe began some 15 billion years ago in an extraordinary moment they call the big bang. Initially, the temperature must have been inconceivably high, but after 1 second, it had dropped to 10 billion K about and subatomic particles began to form: protons, neutrons, and electrons. After 3 minutes, the temperature had dropped to 1 Billion K and protons began fusing with neutrons to form helium nuclei. Matter remained in this form for many millions of years until the expanding universe had cooled to about 10,000 K and electrons were then able to bind to protons and to helium nuclei, forming stable hydrogen and helium atoms.
The attractive force of gravity acting on regions of higher than-average density slowly produced massive local concentrations of matter and ultimately formed billions of galaxies, each with many billions of stars. As the gas clouds of hydrogen and helium condensed under gravitational attraction and stars formed, their temperatures reached 10 million K and their densities reached 100 g / cubic centimeter. Protons and neutrons again fused to yield helium nuclei, generating vast amounts of heat and light. Most of these early stars probably burned out after a few billion years, but a few were so massive that, as their nuclear fuel diminished, gravitational attraction caused a rapid contraction leading to still higher core temperatures and higher densities up to 50 million K and 0.5 million gr / cubic centimeter. Under such extreme conditions, larger nuclei were formed, including carbon, oxygen, silicon, magnesium, and iron. Ultimately, the stars underwent a gravitational collapse resulting in the synthesis of still heavier elements and an explosion visible throughout the universe as a supernova. Matter from exploding supernovas was blown throughout the galaxy, forming a new generation of stars and planets. Our own sun and solar system formed about 4.5 billion years ago from matter released by former supernovas. Except for hydrogen and helium, all the atoms in our bodies and our entire solar system were created more than five billion years ago in exploding stars. We and our world are made from the ashes of dying stars.
ANAΔΗΜΟΣΙΕΥΣΗ ΑΠΟ ΤΟ ΒΙΒΛΙΟ "Fundamentals of General, Organic, and Biological Chemistry" SIXTH EDITION ΤΩΝ John McMurry Cornell University
Mary Castellion Norwalk,Connecticut
29/2/2016
The attractive force of gravity acting on regions of higher than-average density slowly produced massive local concentrations of matter and ultimately formed billions of galaxies, each with many billions of stars. As the gas clouds of hydrogen and helium condensed under gravitational attraction and stars formed, their temperatures reached 10 million K and their densities reached 100 g / cubic centimeter. Protons and neutrons again fused to yield helium nuclei, generating vast amounts of heat and light. Most of these early stars probably burned out after a few billion years, but a few were so massive that, as their nuclear fuel diminished, gravitational attraction caused a rapid contraction leading to still higher core temperatures and higher densities up to 50 million K and 0.5 million gr / cubic centimeter. Under such extreme conditions, larger nuclei were formed, including carbon, oxygen, silicon, magnesium, and iron. Ultimately, the stars underwent a gravitational collapse resulting in the synthesis of still heavier elements and an explosion visible throughout the universe as a supernova. Matter from exploding supernovas was blown throughout the galaxy, forming a new generation of stars and planets. Our own sun and solar system formed about 4.5 billion years ago from matter released by former supernovas. Except for hydrogen and helium, all the atoms in our bodies and our entire solar system were created more than five billion years ago in exploding stars. We and our world are made from the ashes of dying stars.
ANAΔΗΜΟΣΙΕΥΣΗ ΑΠΟ ΤΟ ΒΙΒΛΙΟ "Fundamentals of General, Organic, and Biological Chemistry" SIXTH EDITION ΤΩΝ John McMurry Cornell University
Mary Castellion Norwalk,Connecticut
29/2/2016
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