Atomic Structure
An atom is the basic building block of all matter and is composed of 3 principle particles: protons, neutrons and electrons. Each atom is made up of a combination of these elementary particles and help to determine the molecular structures that atoms can combine to form. Protons are positively charged and resides in the nucleus of an atom. The neutron is of a neutral charge (not positive or negative) and also resides in the nucleus of an atom. The electron is significantly smaller than the proton or neutron particles, and remains outside of the nucleus surrounding the center at various energy levels.
Centrifugal Force
Since the proton and electron are attracted to one another because of their opposite charges, what is there to keep the two from colliding? Well, the centrifugal force of the rotating electron around the center, or nucleus, keeps the two from crashing. The same force that works on the planets in our solar system from colliding with the sun also works within and forms the atomic structure.
Electron Cloud
Most of us have seen an illustration of electrons around the nucleus of the atom represented as tiny dots in different orbits. This demonstration is actually a bit misleading and should portray the electrons around the nucleus as a cloud. Electrons have many of the same properties as a wave and thus, this continuously moving wave of negatively charged electrons surrounds the center of an atom as an electron cloud.
Nuclear Glue
If an atom has the same number of protons as electrons, the atom is considered to be electrically neutral. A simple example of this neutrality is with the Hydrogen atom which only has one proton (+) and one neutron (-) and the charges from these particles equal (=) an electrically neutral atom. Once we introduce more than one proton into the nucleus of an atom, such as with Helium, the two protons will naturally repel one another. This repellent force would literally tear the nucleus apart. This is where the usefulness of the neutron particles come in. Since the neutrons have no electrical charge they hold the protons in the nucleus together by acting as a sort of "nuclear glue".