Final Answer:
Here is the completed chart:
| Symbol | Atomic number | Number of Protons | Mass number | Number of neutrons |
|------------|---------------|-------------------|-----------|--------------------|
| ¹H | 1 | 1 | 1 | 0 |
| ²H | 1 | 1 | 2 | 1 |
| ³H | 1 | 1 | 3 | 2 |
| ⁴He | 2 | 2 | 4 | 2 |
| ¹²C | 6 | 6 | 12 | 6 |
| ¹⁴C | 6 | 6 | 14 | 8 |
| ¹⁸O | 8 | 8 | 18 | 10 |
| ⁴⁹Sc | 21 | 21 | 49 | 28 |
| ⁶³Co | 27 | 27 | 63 | 36 |
| ²¹²Pb | 82 | 82 | 212 | 130 |
| ²²²Ra | 88 | 88 | 222 | 134 |
| ²²⁶Ra | 88 | 88 | 226 | 138 |
| ²³⁵U | 92 | 92 | 235 | 143 |
| ²³⁸U | 92 | 92 | 238 | 146 |
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Explanation:
Let’s go step by step so you can fill in any chart like this.
1.
Atomic number = Number of protons
The small number at the bottom left (like the “1” in ¹H) is the atomic number. That’s also how many protons the atom has. So if you see ¹H, atomic number = 1 → protons = 1.
2.
Mass number = Protons + Neutrons
The big number on top (like the “1” in ¹H) is the mass number. That’s the total of protons and neutrons.
3.
To find neutrons: Mass number – Protons
Example: For ⁴He, mass number = 4, protons = 2 → neutrons = 4 – 2 = 2.
Let’s do one row together — ¹⁴C:
- Symbol is ¹⁴C → the bottom number is 6 → atomic number = 6 → protons = 6.
- Top number is 14 → mass number = 14.
- Neutrons = 14 – 6 = 8.
That’s it! Just repeat for each row.
You might notice some symbols have the same atomic number but different mass numbers — those are isotopes (same element, different neutrons).
Try filling in ³H:
- Bottom number = 1 → atomic number = 1 → protons = 1.
- Top number = 3 → mass number = 3.
- Neutrons = 3 – 1 = 2.
See? Easy once you know the trick!
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Parent Tip: Review the logic above to help your child master the concept of isotope worksheet.
