Counting Atoms in Compounds Worksheet - Flying Colors Science - Free Printable

To solve this worksheet, we need to look at the chemical formula for each substance and count how many atoms of each element are present.

How to count atoms in a formula:
1. Identify the elements: Look at the capital letters (e.g., H is Hydrogen, O is Oxygen).
2. Check for subscripts: The small number written to the bottom right of an element symbol tells you how many atoms of that element there are.
* If there is no number, it means there is 1 atom.
* Example: In $H_2O$, the '2' next to H means 2 Hydrogens. There is no number next to O, so there is 1 Oxygen.
3. Check for parentheses: If you see brackets like $(OH)_2$, the number outside multiplies everything inside.
* Example: $Mg(OH)_2$ has 1 Magnesium, and $1 \times 2 = 2$ Oxygens, and $1 \times 2 = 2$ Hydrogens.

Here is the step-by-step breakdown for each row in the "Part One" table:

1. Nitric Acid ($HNO_3$)
* H: No subscript $\rightarrow$ 1
* N: No subscript $\rightarrow$ 1
* O: Subscript is 3 $\rightarrow$ 3
* *Count:* Hydrogen - 1, Nitrogen - 1, Oxygen - 3

2. Acetic Acid ($HC_2H_3O_2$)
* *Note:* This formula lists Hydrogen twice. We add them together.
* H: $1 + 3 = 4$
* C: Subscript is 2 $\rightarrow$ 2
* O: Subscript is 2 $\rightarrow$ 2
* *Count:* Hydrogen - 4, Carbon - 2, Oxygen - 2

3. Sodium Silicate ($Na_2SiO_3$)
* Na: Subscript is 2 $\rightarrow$ 2
* Si: No subscript $\rightarrow$ 1
* O: Subscript is 3 $\rightarrow$ 3
* *Count:* Sodium - 2, Silicon - 1, Oxygen - 3

4. Water ($H_2O$)
* H: Subscript is 2 $\rightarrow$ 2
* O: No subscript $\rightarrow$ 1
* *Count:* Hydrogen - 2, Oxygen - 1

5. Vitamin C ($C_6H_8O_6$)
* C: Subscript is 6 $\rightarrow$ 6
* H: Subscript is 8 $\rightarrow$ 8
* O: Subscript is 6 $\rightarrow$ 6
* *Count:* Carbon - 6, Hydrogen - 8, Oxygen - 6

6. Aspirin ($C_9H_8O_4$)
* C: Subscript is 9 $\rightarrow$ 9
* H: Subscript is 8 $\rightarrow$ 8
* O: Subscript is 4 $\rightarrow$ 4
* *Count:* Carbon - 9, Hydrogen - 8, Oxygen - 4

7. Chloroform ($CHCl_3$)
* C: No subscript $\rightarrow$ 1
* H: No subscript $\rightarrow$ 1
* Cl: Subscript is 3 $\rightarrow$ 3
* *Count:* Carbon - 1, Hydrogen - 1, Chlorine - 3

8. Glucose ($C_6H_{12}O_6$)
* C: Subscript is 6 $\rightarrow$ 6
* H: Subscript is 12 $\rightarrow$ 12
* O: Subscript is 6 $\rightarrow$ 6
* *Count:* Carbon - 6, Hydrogen - 12, Oxygen - 6

Final Answer:
Nitric Acid: Hydrogen - 1, Nitrogen - 1, Oxygen - 3
Acetic Acid: Hydrogen - 4, Carbon - 2, Oxygen - 2
Sodium Silicate: Sodium - 2, Silicon - 1, Oxygen - 3
Water: Hydrogen - 2, Oxygen - 1
Vitamin C: Carbon - 6, Hydrogen - 8, Oxygen - 6
Aspirin: Carbon - 9, Hydrogen - 8, Oxygen - 4
Chloroform: Carbon - 1, Hydrogen - 1, Chlorine - 3
Glucose: Carbon - 6, Hydrogen - 12, Oxygen - 6