Elements are the basic building blocks of the environment
we see. This does not mean, however, that they are indivisible. Elements
are the smallest unit of matter that retains its properties. They
are composed of one type of atom. The numbers of protons, neutrons
and electrons they contain determine their characteristics. The lightest
element is hydrogen, which is composed of one proton and one electron.
There are 92 naturally occurring elements and many more which are
man-made, such as plutonium. Elements combine in various ways to create
the world and universe we perceive today.
The most abundant element in the universe is hydrogen, most likely
due to its simplicity. Hydrogen serves as the fuel for stars during
most of their lives. The stars burn this hydrogen, through fusion,
and create helium, which is the second lightest element. As the star,
after many years (between millions and billions), burns up all of
its hydrogen fuel, the helium that was the byproduct from the above
begins to be burned into other, heavier elements. Once the star eventually
reaches a stage where iron is produced, there is a lack of energy
to counter-balance the force of gravity. The equilibrium is broken
and the star begins to contract forming various objects (mentioned
in other articles).
As the star explodes, all of the various heavy elements produced in
its death stages are expelled into space. These serve as the building
blocks for objects such as planets, asteroids and more. This is where
the popular maxim, "we are made of star stuff ," comes from.