are the building blocks of everything around us, including our earth,
the sun, and all other planets in the universe. Amazingly, there
are just over 100 types of atoms that make up all matter. Each type
of atom has a particular number of protons and electrons. It is
the number of protons that makes each type of atom unique. (Each
unique type of atom is called an .)
of an Atom
Atoms are made up of three main parts: neutrons, protons, and electrons.
The neutrons and protons join together to form the nucleus of an
atom. The electrons spin around the nucleus.
Fifty million atoms lined up would measure one millimeter
Protons and electrons are very interesting. They carry a charge.
That is, they are either attracted to or repelled by each other.
Protons carry a positive charge. Electrons carry a negative charge.
Neutrons don't carry any charge; they are neutral. Opposite charges
attract. Like charges repel. A neutral charge will pair up with
are what allow the electron to spin in orbit around the nucleus.
The electrons are attracted to the nucleus because the positively
charged protons are there.
Some atoms are unstable. The nucleus has too many or too few protons.
Sometimes this will cause the atom to shoot out part of its nucleus
in the form of . These particles of radiation are , beta particles, and alpha particles.
Alpha particles contain two protons and two neutrons. Beta
particles are electrons. Gamma rays are invisible rays (like
Of the three types of radiation, beta particles and gamma rays
are dangerous to humans and other organisms. Beta particles
can be stopped by a sheet of aluminum. Gamma rays can be stopped
by a thick sheet of lead or concrete. Alpha particles are stopped
Radioactive elements are used to generate nuclear energy and to
create nuclear weapons. It takes very little of a radioactive element
to produce a lot of energy.
Table of Elements
Check out the different types of atoms that make up our universe
with the interactive Periodic
Table of Elements on the Los Alamos National Laboratory's Chemistry
Division Web site.