An element is a species of atoms having the same amount of protons in their atomic nuclei. All matter is made up of elements. An element is considered a pure substance, because within all elements, atomic structure is the same. 118 Elements have been identified, 94 of these naturally occurring, and 24 man-made. Elements are identified by their Atomic Number, Atomic Mass, Name, and Symbol. Elements are all on the periodic table, which orders them by their atomic number, and places them in groups, or rows, based on their number of valence electrons. The more valence electrons an atom has, the less reactive it is. Some examples of elements are Oxygen(in its pure form), Gold, Sodium, and Carbon.
A compound is composed of two or more elements that are chemically bonded. There are currently about ten million known compounds. Compounds are still considered pure substances, because within a group of the same compound, all characteristics are the same. Most of what we know is made up of compounds. Some examples of compounds are oxygen(in its natural state), water, and salt.
A mixture is made up of two or more elements or compounds together that are not chemically bonded. There are two types of mixtures: Homogeneous and Heterogeneous. a homogeneous mixture has uniform composition throughout its mass, while a heterogeneous mixture does not. An example of a homogeneous mixture would be air or Pepsi, and an example of a heterogeneous mixture would be soil or rocks.