preAP Chem 2013-2014 1 Name ________________________________ Note: It is very important that you note that some elements do not occur as single atoms when by themselves. If they are not combined with another element, they will bond with themselves, forming a _________________ molecule. In any chemical reaction, when you see these elements alone, they must be shown with a diatomic formula. Diatomic elements: H2, N2, O2, F2, Cl2, Br2, I2 I. Describing Chemical Change A. Writing Equations ? words can be used to describe _____________________________, but that can become long and ______________________. ? chemists use ___________________________ to describe reactions. In chemical equations,