A compound can be separated into the individual elements that it is comprised of and an element can separated as far as its individual atoms. An atom represents the smallest possible part of an element that still retains the properties of that element. The sub-atomic particles that represent the individual components of an atom no longer possess the same properties as the element from which they came.
Compounds are substances that are created when two or more elements are chemically joined. The atoms of those elements attach to each other by chemical bonds. When elements bond in this manner to form compounds, they lose their individual properties and take on the new properties of the compound that their bonding creates.
The three primary sub-atomic particles that comprise the individual atoms of an element are protons, neutrons and electrons. The electrons orbit a nucleus in which the neutrons and protons are compacted into a mass that represents more than 99.94 percent of the atom's mass. The number of electrons and electron orbits play a major role in how atoms bond with other atoms. The most significant role in chemical bonding belongs to the electrons orbiting in the atom's outermost layer, or shell. These are called the valence electrons and their number determines how the atom will interact with other atoms. The tendency of an atom is to fill or empty its valence shell and it will react with another atom in a manner that depends upon that other atom's specific valence shell configuration.