Environmental Yellow Pages

The Atom
All macroscopic matter is made out of many miniscule particles called atoms. The study of how these atoms interact is called Chemistry.
Subatomic Particles
The three particles that make up atoms are protons, neutrons, and electrons. Protons and neutrons are the heavier particles that reside in the nucleus, the dense center of the atom. Electrons are extremely lightweight and negatively charged particles that exist in the electron cloud that surrounds the atom with a radius 10,000 times greater than the nucleus itself.
The Nucleus
The nucleus of the atom is the dense center made of an atom's protrons and neutrons. Virtually all the mass of the atom resides in the nucleus. The nucleus is held together by the tight pull of what is known to Physicists as the Strong force. This force between the nucleons overcomes the repulsive electrical force that would push the protons apart.
Electrons
The electron is the lightweight particle that exists "in orbit" at great distances outside of the atomic nucleus. Chemical interactions are essentially electron interactions of two atoms. The magnitude of the charge on an electron is equal to the charge on a protron. Electrons surround the atom in pathways called orbitals. The inner orbitals surrounding the atom are spherical but the outer orbitals are much more complicated.
Chemical Bonding
Chemically bonding occurs when two particles can exchange or combine their outer electrons in such a way that is energetically favorable. This is analogous to an airborn rock's natural tendancy to fall to the floor -- The rock has less potential energy when it is near the ground than when it is high because a higher rock can gain more speed (kinetic energy) before hitting the ground.