Protons, Neutrons, and Electrons Practice Worksheet for students to calculate subatomic particle counts based on given atomic data.

Let's solve the Protons, Neutrons, and Electrons Practice Worksheet step by step.

We are given a table with various elements and asked to fill in missing values for:

- Atomic Number (Z): Number of protons
- Mass Number (A): Protons + Neutrons
- Number of Protons
- Number of Neutrons
- Number of Electrons

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🔍 Key Concepts:

1. Atomic Number (Z) = Number of protons
2. Mass Number (A) = Protons + Neutrons → So, Neutrons = A - Z
3. Electrons = Protons (in neutral atoms)
4. Element symbol and name help identify atomic number (from periodic table)

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Let’s go row by row and fill in the blanks.

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1. Boron

- Symbol: B
- Mass Number: 11
- Atomic Number: ?
- Protons: ?
- Neutrons: 6
- Electrons: ?

From periodic table: Boron (B) has atomic number = 5

So:
- Protons = 5
- Mass = 11 → Neutrons = 11 - 5 = 6 ✔ (matches)
- Electrons = 5 (neutral atom)

✔ All match.

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2. Beryllium

- Symbol: Be
- Mass Number: 11
- Atomic Number: ?
- Protons: ?
- Neutrons: 7
- Electrons: ?

From periodic table: Be has atomic number = 4

So:
- Protons = 4
- Neutrons = 7 → Mass = Protons + Neutrons = 4 + 7 = 11 ✔
- Electrons = 4

✔ All good.

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3. Gallium

- Symbol: Ga
- Mass Number: ?
- Atomic Number: 31
- Protons: 31
- Neutrons: 39
- Electrons: ?

Atomic number = 31 → Protons = 31, Electrons = 31 ✔

Mass = Protons + Neutrons = 31 + 39 = 70

So:
- Mass Number = 70

✔ Done.

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4. Copper

- Symbol: Cu
- Mass Number: 64
- Atomic Number: ?
- Protons: 29
- Neutrons: 35
- Electrons: ?

Protons = 29 → Atomic number = 29 (Copper) ✔

Neutrons = 35 → Mass = 29 + 35 = 64 ✔

Electrons = 29 (neutral atom)

✔ All correct.

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5. Tin (Sn)

- Symbol: Sn
- Mass Number: 120
- Atomic Number: ?
- Protons: ?
- Neutrons: ?
- Electrons: ?

Tin (Sn) has atomic number = 50 → Protons = 50, Electrons = 50

Mass = 120 → Neutrons = 120 - 50 = 70

So:
- Atomic Number = 50
- Protons = 50
- Neutrons = 70
- Electrons = 50

✔ Done.

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6. Ytterbium

- Symbol: Yb
- Mass Number: 173
- Atomic Number: ?
- Protons: ?
- Neutrons: 102
- Electrons: ?

Ytterbium (Yb) has atomic number = 70

So:
- Protons = 70
- Electrons = 70
- Neutrons = 102 → Mass = 70 + 102 = 172 ✘ But mass is given as 173

Wait! That’s inconsistent.

But we’re told mass number = 173, neutrons = 102 → then protons = 173 - 102 = 71

But Yb atomic number is 70, not 71.

Hmm — contradiction?

Wait — perhaps this is an isotope? Let's check.

If mass = 173, neutrons = 102, then protons = 173 - 102 = 71

Element with atomic number 71 is Lutetium (Lu), not Yb.

But the symbol says Yb.

This suggests a mistake either in the problem or in our assumption.

Wait — let's double-check:

Yb (Ytterbium) has atomic number 70.

Common isotopes: Yb-172, Yb-173, etc.

So if it's Yb-173, then:
- Mass = 173
- Protons = 70
- Neutrons = 173 - 70 = 103

But here, neutrons = 102 → that would mean protons = 173 - 102 = 71 → Lu

So either:
- The symbol is wrong, or
- The neutron count is wrong

But since the symbol is Yb, and atomic number should be 70, then:
- Protons = 70
- Electrons = 70
- Neutrons = 173 - 70 = 103

But the table says neutrons = 102 → conflict.

Wait — look at the table again:

> Ytterbium
> Mass: 173
> Neutrons: 102
> Protons: ?
> Electrons: ?

So:
- If mass = 173, neutrons = 102 → protons = 173 - 102 = 71

But Ytterbium is atomic number 70.

So unless it's a typo, this can't be Yb.

Possibility: It might be Lutetium (Lu), atomic number 71.

But the name says "Ytterbium".

So likely a typo in the worksheet.

But let's assume the data is correct and the element is Yb, then:

- Atomic number = 70
- Protons = 70
- Electrons = 70
- Mass = 173 → Neutrons = 173 - 70 = 103

But the table says neutrons = 102 → so maybe the mass is wrong?

Alternatively, maybe it's Yb-172?

Wait — the mass is clearly written as 173.

So the only way this works is if:
- Protons = 71 → Lu
- But named Yb → error

So likely typo in neutron count.

But since the question asks us to fill in based on the given data, let's proceed with the numbers.

Given:
- Mass = 173
- Neutrons = 102
→ Protons = 173 - 102 = 71
→ Element with atomic number 71 is Lutetium (Lu), not Yb

So either:
- Symbol is wrong, or
- Neutrons are wrong

But since the name is "Ytterbium", and it's known that Yb-173 exists with 70 protons and 103 neutrons, then the neutron count must be 103, not 102.

So probably a typo in the worksheet.

But we have to work with what's given.

Wait — looking back at the original image:

> Ytterbium
> Mass: 173
> Neutrons: 102
> Protons: ?
> Electrons: ?

So from data:
- Protons = 173 - 102 = 71
- Electrons = 71 (if neutral)
- Atomic number = 71 → Lutetium (Lu), not Yb

So either the name or symbol is wrong.

But since the name is "Ytterbium", and symbol is Yb, we’ll assume the neutron count is incorrect.

But perhaps in this context, we are to use the formula regardless.

Let’s suppose we accept the given numbers:

- Mass = 173
- Neutrons = 102 → Protons = 71
- So atomic number = 71
- Electrons = 71

But then it's not Yb.

So this row has conflicting information.

But maybe I misread — let me check the actual table again.

Wait — in your uploaded image, it says:

> Ytterbium
> Mass: 173
> Neutrons: 102
> Protons: ?
> Electrons: ?

And no atomic number given.

So we can compute:
- Protons = Mass - Neutrons = 173 - 102 = 71
- Electrons = 71 (assuming neutral)
- Atomic number = 71 → Lutetium, not Ytterbium

So error in the name — should be Lutetium.

But since the worksheet says "Ytterbium", we'll note the discrepancy.

But for now, let’s fill in based on numbers:

- Protons = 71
- Electrons = 71
- Atomic number = 71

But the element name is wrong.

We’ll continue and flag it.

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7. Arsenic (As)

- Symbol: As
- Mass Number: 75
- Atomic Number: ?
- Protons: ?
- Neutrons: 42
- Electrons: ?

Mass = 75, Neutrons = 42 → Protons = 75 - 42 = 33

Arsenic (As) has atomic number 33 → matches ✔

Electrons = 33

✔ All good.

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8. Thallium

- Symbol: Tl
- Mass Number: 204
- Atomic Number: 81
- Protons: ?
- Neutrons: ?
- Electrons: ?

Atomic number = 81 → Protons = 81, Electrons = 81

Mass = 204 → Neutrons = 204 - 81 = 123

But table says 120 — wait, it says 120?

Look:

> Thallium
> Mass: 204
> Atomic Number: 81
> Protons: ?
> Neutrons: 120
> Electrons: ?

But 204 - 81 = 123 → Neutrons should be 123, not 120

So neutron count is wrong.

Or mass is wrong?

But mass is 204 — common isotope of Tl is Tl-204 (yes, exists), with 81 protons, 123 neutrons.

So neutrons should be 123, not 120.

So another error in worksheet.

But we have to go with what's given?

No — we use logic.

Given:
- Mass = 204
- Atomic number = 81
→ Protons = 81
→ Neutrons = 204 - 81 = 123
→ Electrons = 81

So table says neutrons = 120 — that’s incorrect.

So we override.

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9. Francium (Fr)

- Symbol: Fr
- Mass Number: 220
- Atomic Number: ?
- Protons: ?
- Neutrons: 137
- Electrons: ?

Mass = 220, Neutrons = 137 → Protons = 220 - 137 = 83

Francium (Fr) has atomic number 87, not 83.

83 is Bismuth (Bi)

So inconsistency.

But Fr-220 would have:
- Protons = 87
- Neutrons = 220 - 87 = 133

But table says 137 neutrons → too many.

So either:
- Mass is wrong, or
- Neutrons are wrong, or
- Element is wrong

But symbol is Fr.

So likely neutrons = 133, but table says 137 → error.

But let's compute:
- Protons = 220 - 137 = 83 → Bi
- But symbol is Fr → contradiction

So again, data conflict

We'll proceed with correct values.

For Fr:
- Atomic number = 87
- Protons = 87
- Electrons = 87
- Mass = 220 → Neutrons = 220 - 87 = 133

So table says 137 → error.

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10. Carbon

- Symbol: C
- Mass Number: ?
- Atomic Number: 12
- Protons: ?
- Neutrons: 6
- Electrons: ?

Carbon has atomic number 12 → Protons = 12, Electrons = 12

Neutrons = 6 → Mass = 12 + 6 = 18

But most common carbon isotope is C-12 (6 protons, 6 neutrons)

But here, neutrons = 6 → mass = 12 + 6 = 18 → C-18?

But atomic number is 12 → yes, possible isotope.

But mass number = 18

So:
- Mass Number = 18

✔

But usually, carbon-12 has 6 neutrons, mass 12.

Here, neutrons = 6, atomic number = 12 → mass = 18 → carbon-18, which is unstable.

But mathematically valid.

So:
- Mass Number = 18

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11. Barium (Ba)

- Symbol: Ba
- Mass Number: ?
- Atomic Number: ?
- Protons: 56
- Neutrons: 84
- Electrons: ?

Protons = 56 → atomic number = 56 → Barium ✔

Electrons = 56

Mass = Protons + Neutrons = 56 + 84 = 140

So:
- Mass Number = 140
- Atomic Number = 56

✔

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12. Calcium (Ca)

- Symbol: Ca
- Mass Number: ?
- Atomic Number: ?
- Protons: 20
- Neutrons: 20
- Electrons: ?

Protons = 20 → atomic number = 20 → Calcium ✔

Electrons = 20

Mass = 20 + 20 = 40

So:
- Mass Number = 40
- Atomic Number = 20

✔

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13. Silver (Ag)

- Symbol: Ag
- Mass Number: ?
- Atomic Number: ?
- Protons: ?
- Neutrons: 62
- Electrons: 47

Electrons = 47 → neutral atom → Protons = 47

Atomic number = 47 → Silver ✔

Mass = Protons + Neutrons = 47 + 62 = 109

So:
- Mass Number = 109
- Atomic Number = 47
- Protons = 47

✔

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14. Magnesium (Mg)

- Symbol: Mg
- Mass Number: 24
- Atomic Number: 12
- Protons: ?
- Neutrons: ?
- Electrons: ?

Atomic number = 12 → Protons = 12, Electrons = 12

Mass = 24 → Neutrons = 24 - 12 = 12

So:
- Protons = 12
- Neutrons = 12
- Electrons = 12

✔

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Final Table with Corrected Values

| Name of Element | Symbol | Mass Number | Atomic Number | Protons | Neutrons | Electrons |
|------------------|--------|-------------|---------------|---------|----------|-----------|
| Boron | B | 11 | 5 | 5 | 6 | 5 |
| Beryllium | Be | 11 | 4 | 4 | 7 | 4 |
| Gallium | Ga | 70 | 31 | 31 | 39 | 31 |
| Copper | Cu | 64 | 29 | 29 | 35 | 29 |
| Tin | Sn | 120 | 50 | 50 | 70 | 50 |
| Ytterbium | Yb | 173 | 70 | 70 | 103 | 70 | ← Corrected: Neutrons = 103
| Arsenic | As | 75 | 33 | 33 | 42 | 33 |
| Thallium | Tl | 204 | 81 | 81 | 123 | 81 | ← Corrected: Neutrons = 123
| Francium | Fr | 220 | 87 | 87 | 133 | 87 | ← Corrected: Neutrons = 133
| Carbon | C | 18 | 12 | 12 | 6 | 12 |
| Barium | Ba | 140 | 56 | 56 | 84 | 56 |
| Calcium | Ca | 40 | 20 | 20 | 20 | 20 |
| Silver | Ag | 109 | 47 | 47 | 62 | 47 |
| Magnesium | Mg | 24 | 12 | 12 | 12 | 12 |

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✔ Summary of Corrections:

- Ytterbium: Neutrons should be 103, not 102 (since 173 - 70 = 103)
- Thallium: Neutrons should be 123, not 120 (204 - 81 = 123)
- Francium: Neutrons should be 133, not 137 (220 - 87 = 133)
- Carbon: Mass number = 18 (12 + 6), not 12 (but possible isotope)

Note: These corrections assume neutral atoms and standard periodic table values.

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Final Answer:

Fill the table using:
- Protons = Atomic Number
- Neutrons = Mass Number - Protons
- Electrons = Protons (for neutral atoms)

The corrected values are shown above.

If you're expected to use only the given data, then some entries will be inconsistent due to errors in the worksheet.

But logically, the correct values are as above.

Let me know if you'd like a cleaned-up version of the completed table.