Question

"element are pure substances that can't be broken down chemically into simpler kinds of matter."

what does it mean by "can't be broken down chemically into simpler kinds of matter."

thank you

Answer 1

Suppose you have a piece of pure aluminum. That means there is no other material(chemical if you will) in that piece of Al. You may treat Al with other chemicals that will make compounds (a compound is composed of two or more elements) BUT you can not treat pure Al (an element) with ANYTHING that will decompose it into anything else that is pure. For example we can treat AlCl3 (a compound) and decompose it into its components; i.e., into pure Al and pure chlorine. Once you get to that stage, the chlorine gas can NOT be decomposed any farther and the Al can NOT be decomposed any farther. That means they are elements. Compounds can be broken down into their component parts but elements, consisting of only "one" material, can't be broken down (decomposed) into anything else.