Cappy Severson, age 12, of Rockford, Illinois, for his question:

Is aluminum an element?

A substance may be an element, a compound or a mixture of several compounds. These differences, of course, take us down to the world of atoms and molecules. An element is made of atoms all of one kind. A compound is made of molecule packages of assorted atoms. The number of different atoms and their elements is limited to roughly 100, and one of these elements is the shiny gray metal we call aluminum. It was discovered in 1825 and for years it was rated among the world's most precious metals. This was because no one had learned a cheap and easy way to separate the element from its mineral ores.

An element has an atomic number, taken from the number of protons in the nucleus of its atom. This number also equals the number of electrons expected to orbit its nucleus. Aluminum has the atomic number 13, meaning that its basic atom has 13 protons and 13 electrons. Chemists group it in a family of elements that share certain features with both metallic and non metallic atomic elements.