Let's solve each problem step by step based on the
Counting Atoms Worksheet instructions:
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Directions Recap:
1. List the elements in each compound.
2. Count how many atoms of each element are present.
3. Add up the total number of atoms.
4. If there’s a coefficient (number) in front of the compound, multiply all atom counts by that number.
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We'll go through each one:
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1) 3NaOH
- Elements: Na, O, H
- In
one NaOH:
- Na = 1
- O = 1
- H = 1
- Multiply by 3 (coefficient):
- Na = 3 × 1 =
3
- O = 3 × 1 =
3
- H = 3 × 1 =
3
- Total atoms = 3 + 3 + 3 =
9
✔ Answer:
Na = 3
O = 3
H = 3
Total =
9 atoms
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2) 4MgCl₂
- Elements: Mg, Cl
- In
one MgCl₂:
- Mg = 1
- Cl = 2
- Multiply by 4:
- Mg = 4 × 1 =
4
- Cl = 4 × 2 =
8
- Total atoms = 4 + 8 =
12
✔ Answer:
Mg = 4
Cl = 8
Total =
12 atoms
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3) Li₂SO₄
- Elements: Li, S, O
- No coefficient → use formula as is
- Li = 2
- S = 1
- O = 4
- Total = 2 + 1 + 4 =
7
✔ Answer:
Li = 2
S = 1
O = 4
Total =
7 atoms
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4) 3NaC₂H₃O₂
- Elements: Na, C, H, O
- In
one NaC₂H₃O₂:
- Na = 1
- C = 2
- H = 3
- O = 2
- Multiply by 3:
- Na = 3 × 1 =
3
- C = 3 × 2 =
6
- H = 3 × 3 =
9
- O = 3 × 2 =
6
- Total = 3 + 6 + 9 + 6 =
24
✔ Answer:
Na = 3
C = 6
H = 9
O = 6
Total =
24 atoms
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5) HNO₃
- Elements: H, N, O
- No coefficient → use as is
- H = 1
- N = 1
- O = 3
- Total = 1 + 1 + 3 =
5
✔ Answer:
H = 1
N = 1
O = 3
Total =
5 atoms
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6) 2Li₂O
- Elements: Li, O
- In
one Li₂O:
- Li = 2
- O = 1
- Multiply by 2:
- Li = 2 × 2 =
4
- O = 2 × 1 =
2
- Total = 4 + 2 =
6
✔ Answer:
Li = 4
O = 2
Total =
6 atoms
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7) H₂O
- Elements: H, O
- No coefficient
- H = 2
- O = 1
- Total = 2 + 1 =
3
✔ Answer:
H = 2
O = 1
Total =
3 atoms
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8) Al₂O₃
- Elements: Al, O
- No coefficient
- Al = 2
- O = 3
- Total = 2 + 3 =
5
✔ Answer:
Al = 2
O = 3
Total =
5 atoms
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✔ Final Answers Summary:
| Problem | Elements | Atom Counts | Total Atoms |
|--------|----------------|----------------------------------|-------------|
| 1) 3NaOH | Na, O, H | Na=3, O=3, H=3 |
9 |
| 2) 4MgCl₂ | Mg, Cl | Mg=4, Cl=8 |
12 |
| 3) Li₂SO₄ | Li, S, O | Li=2, S=1, O=4 |
7 |
| 4) 3NaC₂H₃O₂ | Na, C, H, O | Na=3, C=6, H=9, O=6 |
24 |
| 5) HNO₃ | H, N, O | H=1, N=1, O=3 |
5 |
| 6) 2Li₂O | Li, O | Li=4, O=2 |
6 |
| 7) H₂O | H, O | H=2, O=1 |
3 |
| 8) Al₂O₃ | Al, O | Al=2, O=3 |
5 |
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Let me know if you'd like this formatted as a printable worksheet or need help with balancing equations next!
Parent Tip: Review the logic above to help your child master the concept of atoms worksheet middle school.
