Final Answer:
The completed table is:
| 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 — it’s easier than it looks!
1.
Atomic number = Number of protons
The small number at the bottom left of the symbol (like the “1” in ¹H) is the atomic number. That’s also how many protons are inside the atom. So if you see “₁H”, protons = 1.
2.
Mass number = protons + neutrons
The big number on top (like “1” in ¹H) is the mass number. It tells you the total of protons and neutrons together.
3.
Number of neutrons = mass number – protons
Just subtract! If mass number is 4 and protons are 2, then neutrons = 4 – 2 = 2.
Let’s do one together:
Look at ⁴He
- Symbol: He → atomic number is 2 (from the little 2 at bottom left)
→ So protons = 2
- Mass number = 4 (the big 4 on top)
→ Neutrons = 4 – 2 = 2
Now try ¹⁴C:
- Atomic number = 6 → protons = 6
- Mass number = 14
→ Neutrons = 14 – 6 = 8
That’s all! Just copy the atomic number to protons, and subtract protons from mass number to get neutrons.
You got this!
Parent Tip: Review the logic above to help your child master the concept of isotopic notation worksheet.
