The elements on the periodic
table are not all naturally occurring
All the
elements from atomic number 1 to atomic number 92
(uranium, U) are naturally occurring
OK, element 43 (Technetium, Tc) is only found in very large stars and has not been found on earth in any concentration; elements 85 (Astatine, At) and 87 (Francium, Fr) are found in extremely small amounts on earth; people wishing to study these three elements usually do so by creating them synthetically
All the naturally occurring elements were formed by
nuclear reaction in stars
Nuclear fusion is a process by which atomic nuclei
are subjected to such high energy and pressure that
they fuse together to become a new element
The process of nuclear fusion is what causes the sun
to shine
In the sun four H nuclei combine to form one He
nucleus; the He nucleus has less mass than the four H
nuclei; the ‘missing‘ mass is the energy
that causes the sun to shine
As you probably know, E = mc2; this means
that matter can be changed into energy and that
energy can be changed into matter
Everything on earth is made up of elements formed in
the centers of stars that exploded before the sun was
born
Synthetic Elements
Elements 93-118 were
all created by scientists in the laboratory
These elements are radioactive and rapidly decay to
become lighter elements; this is why they do not occur naturally even though they may actually form as a result of stellar nuclear reactions
Elements can be created by the disintegration of
large nuclei into two or more smaller nuclei; this
process is called fission and occurs on a large scale
in nuclear power reactors
Elements can also be created by bombarding atoms with
other atoms at very high speeds; they can be made to
combine to form a new isotope
Energy and particles such as neutrons,
electrons, positrons, and hydrogen nuclei (protons)
are produced in these nuclear reactions