# Counting Atoms Counting Atoms Bellringer 10/25 1. What was the purpose of the lab we did yesterday? 2. List 2 things you observed happening. 3. Define the Law of Conservation of Mass. How do we

count atoms? Remember! Subscripts are the little numbers that tell us how many atoms there are. EX- H2O Coefficients are regular sized numbers that tell us how many molecules there are. EX- 3NO

How do we count atoms? If there is a chemical compound with only subscripts then its whatever the subscripts tell you! CH4 1 atom of Carbon 4 atoms of Hydrogen If there are both subscripts and

coefficients multiply all the subscripts by the coefficient How do we count atoms? Here are 5 easy steps 1. Write the chemical formula 2. List all the atoms 3. Count the number of atoms of

each element in 1 molecule 4. Multiply the number of atoms of each by the coefficient 5. Make sure your answer makes sense Practice 4C6H12O6 (glucosesugar) C- 4 x 6= 24 H- 4 x 12= 48 O- 4 x 6= 24

Whats the total number of atoms in sugar? 24 + 48+ 24= 96 atoms! Practice 6C2H5OH C- 2 x 6= 12 H- 5 x 6= 30 O- 1 x 6= 6 H- 1 x 6= 6

But wait H appears twice! Thats okay, you want the TOTAL number of H so that means there are 30+6= 36

More Practice 5 Ca(OH)2 Ca- 5 x 1= 5 O- 5 x 2= 10 H- 5 x 2= 10 How many total atoms are in calcium hydroxide? There are 25 atoms total!