Guided Notes 2.5 Diatomic Elements Some elements cannot _________________ by themselves, even when they are isolated from any other type of atom. Elements of this nature will combine with atoms of the ___________________________ in order to be stable. In other words, hydrogen, a diatomic element, cannot be by itself. It cannot exist as simply _______. Hydrogen is so reactive that when isolated from everything but hydrogen it will combine into a diatomic (two atom) molecule. Therefore, hydrogen gas, that is sometimes used as a fuel, exists as __________. The fact that these elements are diatomic is ONLY when they are alone, NOT when chemically bonded to ________________________. When hydrogen is bonded to something other than itself, the numbers of hydrogens depends on the charge of the other atom. There are eight elements that form diatomic molecules, that cannot exist by themselves. High-‐light them on the periodic table below: Chemical Reactions Guided Notes 2.5 There are a number of acronyms or silly ways to remember them. Write down the one you prefer below: Chemical Reactions A chemical reaction is a process in which ___________________________________________ ________________________________________________________________________________________________. When a chemical reaction occurs, the starting materials change, combine or alter themselves into ____________________________________________. A chemical reaction takes place when an atom can find a more stable way to be joined to other atoms. In a chemical reaction, those substances present before the reaction are called the ___________________________. Substances produced in a chemical reaction are called the ___________________________. An example of a chemical reaction would be burning a log. The reactant is a log. The product is the ash and gases produced when burning occurs. Chemical Equations Scientists represent chemical reactions in chemical equations. Chemical equations can be in words or in formulas. In writing equations, many times it is important to know the state of the atom or molecule you are working with. To show this, we use the following abbreviations: (l) -‐ (g) -‐ (s) -‐ (aq) -‐ Aqueous means ____________________________. Chemical Reactions Guided Notes 2.5 Examples: Chemical Reactions