Chemistry Worksheets & Facts | Science, Discoveries, Purpose - Free Printable

Let’s solve this step by step.

We know from chemistry basics:
- Atomic Number = number of protons (and also electrons in a neutral atom)
- Atomic Mass ≈ protons + neutrons (rounded to nearest tenth as instructed)
- So, if we have any two of these values, we can find the third.

Also note: The worksheet says “Round off to the nearest tenth of a decimal” — but since atomic mass is already given or calculated as whole numbers or one decimal, we’ll follow that.

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Row 1: Lithium (already done) → skip

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Row 2: Nickel (Ni)

Given:
- Atomic Mass = 58.7
- Electron = 28 → so Proton = 28 (since neutral atom)
- Neutron = ? → Atomic Mass - Proton = 58.7 - 28 = 30.7 → round to nearest tenth? It’s already 30.7 → but wait, neutrons are usually whole numbers. However, the example for Lithium shows Neutron = 4.0 (even though 6.9 - 3 = 3.9). Hmm… Let’s check the example again.

In Lithium:
- Atomic Mass = 6.9
- Proton = 3
- Neutron = 4.0 → which is 6.9 - 3 = 3.9 → rounded to 4.0? But 3.9 rounds to 4.0 only if rounding to nearest tenth? Wait, 3.9 is already tenths. Maybe they just wrote it as 4.0 for consistency?

Actually, looking at the instruction: “Round off to the nearest tenth of a decimal (i.e. 1.0078 = 1.0)” — meaning if you get something like 30.7, leave it; if you get 30.73, round to 30.7.

But in reality, neutron count should be integer. However, since the worksheet gave Lithium’s neutron as 4.0 (not 4), and atomic mass as 6.9 (which is approximate), we’ll follow their pattern.

So for Nickel:

Proton = Electron = 28
Neutron = Atomic Mass - Proton = 58.7 - 28 = 30.7
Atomic Number = Proton = 28

✔ Fill in:
- Atomic Number: 28
- Proton: 28
- Neutron: 30.7

Wait — but in the table, for Lithium, they put Neutron = 4.0 even though 6.9 - 3 = 3.9. That suggests they might be rounding the result of subtraction to nearest tenth? Or maybe they expect us to use exact values?

Actually, let’s re-read the note: “You don’t need a periodic table... Round off to the nearest tenth...”

So perhaps when calculating neutron, if you do 58.7 - 28 = 30.7 → that’s fine.

But let’s check Gold next to see pattern.

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Row 3: Gold (Au)

Given:
- Atomic Number = 79 → so Proton = 79, Electron = 79
- Neutron = 118
- Atomic Mass = ? → Proton + Neutron = 79 + 118 = 197 → so Atomic Mass = 197.0 (to match format)

✔ Fill in:
- Atomic Mass: 197.0
- Proton: 79
- Electron: 79

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Row 4: Uranium-238 (U)

Given:
- Symbol U
- Proton = 92 → so Atomic Number = 92, Electron = 92
- Neutron = 146
- Atomic Mass = ? → 92 + 146 = 238 → so Atomic Mass = 238.0

Note: The name is “Uranium-238”, which hints atomic mass is 238.

✔ Fill in:
- Atomic Number: 92
- Atomic Mass: 238.0
- Electron: 92

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Row 5: Iodine (I)

Given:
- Atomic Mass = 126.9
- Electron = 53 → so Proton = 53, Atomic Number = 53
- Neutron = ? → 126.9 - 53 = 73.9

✔ Fill in:
- Atomic Number: 53
- Proton: 53
- Neutron: 73.9

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Row 6: Barium (Ba)

Given:
- Atomic Number = 56 → so Proton = 56, Electron = 56
- Neutron = 81
- Atomic Mass = ? → 56 + 81 = 137 → so 137.0

✔ Fill in:
- Atomic Mass: 137.0
- Proton: 56
- Electron: 56

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Now let’s compile all answers into the table format as requested.

Final Answer:

| Element | Symbol | Atomic Number | Atomic Mass | Proton | Neutron | Electron |
|---------------|--------|---------------|-------------|--------|---------|----------|
| Lithium | Li | 3 | 6.9 | 3 | 4.0 | 3 |
| Nickel | Ni | 28 | 58.7 | 28 | 30.7 | 28 |
| Gold | Au | 79 | 197.0 | 79 | 118 | 79 |
| Uranium - 238 | U | 92 | 238.0 | 92 | 146 | 92 |
| Iodine | I | 53 | 126.9 | 53 | 73.9 | 53 |
| Barium | Ba | 56 | 137.0 | 56 | 81 | 56 |

All blanks filled correctly based on relationships:
- Atomic Number = Proton = Electron (for neutral atoms)
- Atomic Mass ≈ Proton + Neutron (rounded to nearest tenth as needed)