Hydrogen and nuclear fusion reactions
Hydrogen is the most common element in the universe, 90% of all matter exists in the form of hydrogen. Helium constitutes the other 10% of matter, which is created from hydrogen through nuclear fusion reactions. It is the fuel of the stars as well as the element from which all other elements are created.
The
most simple atom.
Hydrogen contains one proton
in the nucleus and one electron, with this it is the most simple atom.
Hydrogen has three isotopes, the common hydrogen with
one proton in the nucleus, deuterium or heavy hydrogen with one
proton and one neutron (see animation) and tritium with one proton
and two neutrons, a radioactive gas.
During the Big Bang hydrogen
was created as the first element, after that helium came into being.
All other elements (still) are created inside the nucleus
of the stars (from hydrogen and helium), by means of nuclear fusion
reactions. These elements are released when the stars explode at the
end of their life cycle.
Fuel for
the stars.
Inside
the nucleus of stars, gases are highly compressed by gravitational
force. Because of this the density as well as the temperature (more
than ten million Kelvin) in the nucleus are so high that nuclear fusion
reaction take place. Hydrogen, as deuterium and tritium atoms, fuse to
helium, here matter disappears and enormous quantities of energy
are released (E=mc2). This energy
transports from the nucleus to the surface of the star, where it escapes
as light and heat (electromagnetic
radiation).
All stars have a steady state
period during their life cycle, in which phase they transform hydrogen to
helium. When the hydrogen gets exhausted the star reaches the end of its
life, then the formed helium is transformed into larger elements like carbon,
oxygen or neon.