Before we can balance equations, we need to be able to count the atoms in a compound or molecule. Example: O 2 There are 2 atoms of oxygen in this molecule. MgCl 2 There is 1 atom of Magnesium and 2 atoms of Chlorine. Compounds/Molecules are bonded together. They CANNOT be separated!!

Count the atoms in the compounds/molecules below. Compound/Mole cule CaCl 2 Ca =Cl = K2OK2OK =O = CO 3 C =O =

Coefficients in front of the compound/molecule means that there are multiple compounds/molecules. Subscripts are after an atom and show how many of that particular element are in a compound. For example: 2 H 2 O means that there are two water molecules This is one water molecule. There are 2 Hydrogen and 1 Oxygen. If I have two water molecules, there are 4 Hydrogen and 2 Oxygen

Given the compounds/molecules, fill in the chart PictureCompound/M olecule 2 NO 2 N =O = 3 NH 3 N =H =

Look back at our examples and write a short response to the title of this slide.

Imagine that your equation is on a scale. The left side and the right side must contain the same number of atoms. The left side of our equation is called the reactants. The is like an equal sign. When you see it, say “yields”. The right side of our equation is called the products. Example: 2 H 2 + O 2 yields 2 H 2 O 2 H 2 + O 2 2 H 2 O

H 2 + O 2 = H 2 O H = O = List the reactants side, then list the products side.

H 2 + O 2 = H 2 O H = O = Count the atoms on the reactants side, then count the atoms on the products side.

H 2 + O 2 = H 2 O H =2 H = 2 O =2 O = 1 O on the reactants side has 2 Oxygen atoms, but O on the products side only has 1. Let’s add a COEFFICIENT of 2 in front of the products side. So now, it will look like this: H 2 + O 2 = 2 H 2 O

H = O = After you recount your atoms, is it balanced now? H =2 H = 4 O =2 O = 2 Oxygen is balanced, but now Hydrogen is not. Find the low side, and add a coefficient of 2.

2 H 2 + O 2 = 2 H 2 O H = O = Count your atoms on the reactants side, then count your atoms on the products side. Are they balanced? H =4 H = 4 O =2 O = 2 Yes! They are balanced! We have the same number of atoms on the reactants as products side.

Step 1: List your elements Step 2: Count your atoms Step 3: Find where it is unbalanced Step 4: Add a coefficient and recount your atoms Step 5: Add a coefficient (if necessary) and recount DON’T FORGET!! You can only add coefficients! Never change the subscripts!!