Counting Atoms Worksheet

Counting Atoms Worksheet

Read each question carefully and follow the instructions to determine the number of atoms for each element in the given chemical formulas. Remember to consider both subscripts and coefficients.

1. In a chemical formula, a subscript tells you the number of   of an element in a molecule.

2. A   placed in front of a chemical formula multiplies the number of atoms of each element in the entire compound.

3. If there is no subscript written next to an element, it is assumed to be  .

For each of the following chemical formulas, list the elements present and the number of atoms for each element.

4. H₂O

Hydrogen:   Oxygen:  

5. CO₂

Carbon:   Oxygen:  

6. NaCl

Sodium:   Chlorine:  

For each of the following chemical formulas, list the elements present and the number of atoms for each element, paying close attention to parentheses.

7. Ca(OH)₂

Calcium:   Oxygen:   Hydrogen:  

8. (NH₄)₃PO₄

Nitrogen:   Hydrogen:   Phosphorus:   Oxygen:  

For each of the following chemical formulas, list the elements present and the number of atoms for each element, considering both subscripts and coefficients.

9. 2H₂O

Hydrogen:   Oxygen:  

10. 3CO₂

Carbon:   Oxygen:  

11. 2Mg(NO₃)₂

Magnesium:   Nitrogen:   Oxygen:  

12. How many oxygen atoms are in 4 molecules of H₂SO₄?

13. Which of the following formulas has the most hydrogen atoms?

14. A chemist has 5 molecules of Al₂(SO₄)₃. How many atoms of each element (Aluminum, Sulfur, and Oxygen) are present in total?