Name:___________________________________________ Period_________ Date_________________
Applied Notes: Unit 5A—Counting Atoms
Read each note slide to find the answers to the questions. The questions go in the order of the slides.
1. What is a “subscript” and what does it tell you in chemistry? To help you remember what
subscript means, remember that a submarine is something that goes below the surface of the
water. Look at an example of a subscript and notice how we write the number below the
surface of the line on which it is written.
2. What is a “coefficient” and what does it tell you in chemistry?
3. In each of the following examples, underline the coefficients and circle the subscripts:
H2SO4
Ba(OH)2
4Cu(NO3)2
4K2SO4
2KNO4
3CaCl2
(NH4)PO4
2Ca3(PO4)2
2H2O
4. In H2O, there are ____# of Hydrogens and ______# of Oxygens.
5. When a chemical formula has parentheses, what do you do with the subscript inside the
parentheses and the subscript outside the parentheses (what kind of math)?
6. In the formula Cu(NO3)2 there are _____# of Copper atoms, ______# of Nitrogen atoms and
_____# of Oxygen atoms.
7. In question 6, how is it that you calculated more Oxygen atoms than Copper atoms?
8. In the formula 3CaCl2 there are _______# of molecules of CaCl2 and there are _______# of
atoms ( remember there is a difference between molecules and atoms!)
9. Use the formula 4Cu(NO3)2 to identify the following:
How many Cu in one molecule?____
How many N in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____
10. Use the formula H2SO4 to identify the following:
How many H in one molecule?____
How many S in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____
11. Use the formula 4K2SO4 to identify the following:
How many K in one molecule?____
How many S in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____
12. Use the formula
(NH4)PO4 to identify the following:
How many N in one molecule?____
How many H in one molecule?_____
How many P in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____
13. Use the formula Ba(OH)2 to identify the following:
How many Ba in one molecule?____
How many O in one molecule?_____
How many H in one molecule?_____
How many total atoms in this molecule?_____
14. Use the formula
2KNO4 to identify the following:
How many K in one molecule?____
How many N in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____
15. Use the formula 2Ca3(PO4)2 to identify the following:
How many Ca in one molecule?____
How many P in one molecule?_____
How many O in one molecule?_____
How many total atoms in this molecule?_____