Explain the origin of chemical elements that we found on the Earth.?

Question

Explain the origin of chemical elements that we found on the Earth.?

Answer 1

Basically, all the elements we find on earth are the end products of thermo-nuclear fusion that has taken place in a star.  

Under tremendous gravitational pressure, the hydrogen in a star reaches such a temperature that a nuclear fusion reaction ocurrs; with the hydrogen fusing to form helium, and giving off energy in the form of gamma rays.  This is the reaction that is currently going on in our own sun.

As the hydrogen is used up, the star swells, but eventually collapses again, until the gravitational pressure produces enough heat to fuse the helium into larger atoms of lithium and other elements.  These reactions go on in a step like fashion, with each element giving rise to a more complex one (ie, atoms containing a higher number of protons and neutrons).

Eventually, when the star starts to produce carbon, the gravitational pressure is insufficient to fuse the carbon nuclei, so the reaction stops, and the star then gradually cools to become a red dwarf.  That will happen to our own sun, in a few billion years time.

If the star is larger than the sun, the reaction may extend all the way up to iron.  But to fuse iron, more energy is required than is given off in the nuclear fusion reaction, so even large stars cannot produce elements higher in the periodic table than iron;

If however, the star is very massive; several times larger than the sun; there will be sufficient mass to cause the star to collapse under tremendous pressure, and explode as a supernova; releasing vast amounts of energy.  So great is the energy produced, that all the higher elements in the periodic table are produced as a result; and are scattered out into space.  What is left of the star is a very dense mass of neutrons, called a neutron star.

The elements that are flung out into space may gradually coallesce again under gravitational attraction.  The material will still be mostly hydrogen; with a small amount of other elements.  Stars that contain such materials left over from earlier supernovae are called 'second generation' stars.  Our sun is one such second generation star; which accounts for the heavier elements making up the earth and the other rocky planets.

Stars that are large enough to form supernovae are very unstable, and burn their hydrogen fuel fast, and may explode as a supernova in a few million years ('live fast, die young'), as against our slower evolving sun, which will burn for several billion years, then fizzle out as a red dwarf.

Answer 2

Don't bother answering if you're going to mention God, Airpearl88 wants and deserves facts.