PHYS 101 Lecture Notes - Lecture 2: Actinide, Actinium, Chemical Formula
Document Summary
Hydrogen is explosive, water is not. (remember the zeppelin hindenburg?) Oxygen is required for combustion, water puts out fires! Water is not a chemical element because it is made of two different kinds of atoms. Any pure substance made of atoms of different types is a chemical compound. Carbon (c) oxygen (o) hydrogen (h) nitrogen (n) calcium (cid:894)ca(cid:895) iro(cid:374) (cid:894)fe(cid:895) . Classic case of the whole being greater than the sum of the parts!! To date there are about 118 known different chemical elements. 94 occur naturally and the others have been produced as a result of nuclear reactions in particle accelerators. Of the 118, about 81 are stable (that is, they do not decay radioactively). Each one of the chemical elements is characterized by a number, the atomic number. If two atoms have the same atomic number they are atoms of the same chemical element. We will explain better the atomic number later on.
