1. Content Assignment #1 Counting Atoms Notes Fold your paper in half – leave in notebook Write your notes on the left side and your diagrams and examples on the right Count three lines from the bottom and draw a line. You will write a “SUMMARY” statement at the bottom. Remember to put your name, date, and period AND assignment title at the top right. Leigh Miller, Pillans M.S.

2. Content Assignment #1 Counting Atoms Notes What are subscripts? Subscripts are numbers that –Tell how many atoms of that element are in the molecule –Are written to the RIGHT of the element’s symbol and slightly below the line H 2 O 2 SYMBOL SUBSCRIPT There are two hydrogen atoms and two oxygen atoms shown here.

3. Content Assignment #1 Counting Atoms Notes What are subscripts? Subscripts are numbers that –Tell how many atoms of that element are in the molecule –Are written to the RIGHT of the element’s symbol and slightly below the line H2OH2O SUBSCRIPT There are two hydrogen atoms and ONE oxygen atom shown here.

4. Content Assignment #1 Counting Atoms Notes What are subscripts? Subscripts are numbers that –Tell how many atoms of that element are in the molecule –Are written to the RIGHT of the element’s symbol and slightly below the line H2OH2O CO 2 SUBSCRIPT There is ONE carbon atom and TWO oxygen atoms shown here.

5. Content Assignment #1 Counting Atoms Notes What are coefficients? Coefficients are numbers that –Tell how many molecules are present –Are written to the LEFT of the molecular formula –Are MULTIPLIED by all of the subscripts in the formula 2H 2 O 4CO 2 COEFFICIENT There are two MOLECULES of water and four molecules of carbon dioxide

6. Content Assignment #1 Counting Atoms Notes What are coefficients? Coefficients are numbers that –Tell how many molecules are present –Are written to the LEFT of the molecular formula –Are MULTIPLIED by all of the subscripts in the formula 2H 2 O COEFFICIENT Now MULTIPLY 2 times 2 and 2 times 1.

7. Content Assignment #1 Counting Atoms Notes What are coefficients? Coefficients are numbers that –Tell how many molecules are present –Are written to the LEFT of the molecular formula –Are MULTIPLIED by all of the subscripts in the formula 2H 2 O COEFFICIENT Now you have FOUR atoms of hydrogen and TWO atoms of oxygen.

8. Content Assignment #1 Counting Atoms Notes What are coefficients? Coefficients are numbers that –Tell how many molecules are present –Are written to the LEFT of the molecular formula –Are MULTIPLIED by all of the subscripts in the formula 4CO 2 COEFFICIENT Now MULTIPLY 4 times 1 and 4 times 2.

9. Content Assignment #1 Counting Atoms Notes What are coefficients? Coefficients are numbers that –Tell how many molecules are present –Are written to the LEFT of the molecular formula –Are MULTIPLIED by all of the subscripts in the formula 4CO 2 COEFFICIENT Now you have FOUR carbon atoms and EIGHT oxygen atoms.

10. Guided Practice: Keep your Science Notebook open and copy the following chemical formulas. Count the following atoms in each molecule. Remember: Your test will be Friday, October 24. 1. Ag 2 S _____Silver _____Sulfur 2. H 2 S _____Hydrogen ______Sulfur 3. NaNO 3 ___Sodium ___Nitrogen ___Oxygen 4. 2AgNO 3 ___Silver ____Nitrogen ___Oxygen 5. 7Na 3 PO 4 __Sodium ___Phosphorus__Oxygen

11. Homework: Count the atoms in the following chemical formulas 1. NaCl 2. Cl 2 3. MgCO 3 4. 3HCl 5. MgCl 2 6. H 2 CO 3 7. 4ZnCl 2 8. H 2

12. Homework: Count the atoms in the following chemical formulas 1. NaCl – 1 sodium; 1 chlorine 2. Cl 2 – 2 chlorine atoms 3. MgCO 3 – 1 magnesium; 1 carbon; 3 oxygen 4. 3HCl – 3 hydrogen; 3 chlorine 5. MgCl 2 – 1 magnesium; 2 chlorine 6. H 2 CO 3 – 2 hydrogen; 1 carbon; 3 oxygen 7. 4ZnCl 2 – 4 Zinc; 8 chlorine 8. H 2 – 2 hydrogen