An Element is a chemical substance of a single atomic structure. Elements cannot be divided into smaller substances. The atomic structure of an element is a single atom, with a specific number of protons in the nucleus. A good example of an element is Oxygen, which is both a corrosive and a necessary element of organic life. Oxygen combines with many other elements to form compounds, and has 8 protons in its nucleus, making it Atomic Element #8.
A Compound is a chemical substance of two or more atomic elements. When the atoms of these elements collide, they can stick together, sometimes trading electrons or modifying their own atomic structure to form different elements; many common compounds are simply elements "stuck together" by ionic bonds. A good example of a compound is Water, which is formed from the two Atomic Elements Hydrogen (#1) and Oxygen (#8); each molecule of water contains two hydrogen atoms and one oxygen atom, connected to form a compound, not a new element. Water can be broken down into two separate atomic elements, which then cannot be broken down any further.