Notes #
~- Chemical Formulas and Equations
Because many molecules are very complex, we use symbols and chemical formulas to represent
__ elements and compounds.
Each element on the periodic table is represented by a symbo .. The symbol is either a capital
letter (C for carbon) or a capital letter with a lowercase letter (Co for cobalt). The symbols tell
us what elements are in the molecule.
When elements are chemically combined to form compounds, we have to represent them using a
chemical formula, also known as a molecular formula. Chemical formulas tell you which
elements make up the molecule using symbols, and how many atoms of each element there are in
the molecule using subscripts. For example, the formula for water, H 20, tells us that there are 2
hydrogen and I oxygen atom in one molecule of water.
Anatomy of a Chemical Equation
@C02 + 6 H20 ~ C6H1206 + 6 0~
Reactants (what goes in) -) Products (what you get out)
This is a chemical formula, it represents a molecule. Each element in the molecule is represented
by a symbol (capital letter or capital and lowercase letter C =carbon, Na =sodium).
--ThT~-i;·~-~~-b~~~i}?t--it·t~ii~--y~~-h~-~-~~~y-~t~~;-~ith~-~i~~~;t·~;~-i~--th-~-~~-i~~~1~~--~i-ih-~~~-i-~--i~----i
.!1.?.. ~-~~-s-~~~p_t,_~-~-i~-~1!.. ~~-"~~i?_I~ . !:. ___
__________________________________________________________________ _______________________________________________________j
A chemical equatio_. is the way we represent what is happening in the chemical reaction.
The reactants are similar to the ingredients in a recipe. A recipe tells you what ingredients you
need and how much of each ingredient needs to be added to the recipe. For example if you are
making brownies from a brownie mix, you might represent the chemical reaction like this:
1 box Brownie mix + 2 eggs + 2 Tbsp oil-) 8 servings of"cake like" brownies
If you change the ingredients (reactants) you change the products.
I box Brownie mix+ 1 egg + 2Tbsp oil-) 8 servings of"chewy" brownies
· Notice how there are "coefficients" in recipes too - they tell you how much of each ingredient to
add, as well as how many servings you should expect to get out.