Worksheet on atomic number and mass number with a fill-in-the-blank table and questions.

Let's solve this step by step.

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Step 1: Understanding Key Concepts

- Atomic Number (Z): The number of protons in the nucleus. It defines the element.
- Mass Number (A): The total number of protons and neutrons in the nucleus:
$$
\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}
$$
- Number of Protons: Equal to the atomic number.
- Number of Neutrons: $ \text{Mass Number} - \text{Atomic Number} $
- Neutral Atom: Number of protons = Number of electrons
- Element Identity: Determined solely by the atomic number (number of protons).

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Step 2: Fill in the Chart

We'll go row by row and fill in missing values using the relationships above.

| Element Name | Atomic Number | Number of Protons | Number of Neutrons | Mass Number |
|--------------|----------------|--------------------|---------------------|-------------|
| carbon | 6 | 6 | 6 | 12 |
| | 8 | 8 | 8 | 16 |
| hydrogen | 1 | 1 | 0 | 1 |
| | 2 | 2 | 2 | 4 |
| hydrogen | 1 | 1 | 2 | 3 |
| nitrogen | 7 | 7 | 7 | 14 |
| | 1 | 1 | 1 | 2 |
| | 92 | 92 | 146 | 238 |
| potassium | 19 | 19 | 20 | 39 |
| | 11 | 11 | 12 | 23 |
| | 47 | 47 | 61 | 108 |
| xenon | 54 | 54 | 77 | 131 |
| | 35 | 35 | 45 | 80 |
| | 24 | 24 | 28 | 52 |
| | 16 | 16 | 16 | 32 |
| gold | 79 | 79 | 118 | 197 |
| | 76 | 76 | 114 | 190 |

> Let's explain each row:

1. Carbon: Given mass = 12, atomic number = ? → But we know carbon has atomic number 6, so protons = 6, neutrons = 12 - 6 = 6.
2. Atomic number 8: That’s oxygen. Protons = 8, neutrons = 8 → mass = 8 + 8 = 16
3. Hydrogen: mass = 1, protons = 1 → neutrons = 1 - 1 = 0
4. Protons = 2, mass = 4: So it's helium (atomic number 2), neutrons = 4 - 2 = 2
5. Hydrogen with 2 neutrons: Protons = 1 (hydrogen), neutrons = 2 → mass = 3 → This is deuterium (isotope)
6. Nitrogen: mass = 14, atomic number = 7 → protons = 7, neutrons = 7
7. Mass = 2, neutrons = 1: So protons = 2 - 1 = 1 → Hydrogen again? Wait — but hydrogen can't have 1 proton and 1 neutron and be called hydrogen? Actually, this would be deuterium, which is still hydrogen. But wait: if protons = 1, then atomic number = 1 → hydrogen. Yes. So it's hydrogen with 1 neutron. But earlier we had hydrogen with 0 neutrons. This is fine — isotopes.
8. Atomic number 92, neutrons = 146: Uranium (U). Mass = 92 + 146 = 238
9. Potassium: atomic number = 19, neutrons = 20 → mass = 19 + 20 = 39
10. Atomic number 11, neutrons = 12: Sodium (Na), mass = 11 + 12 = 23
11. Protons = 47, mass = 108: Silver (Ag), atomic number = 47, neutrons = 108 - 47 = 61
12. Xenon: neutrons = 77, mass = 131 → protons = 131 - 77 = 54 → Xenon (Xe)
13. Neutrons = 45, mass = 80: Protons = 80 - 45 = 35 → Bromine (Br)
14. Protons = 24, mass = 52: Chromium (Cr), neutrons = 52 - 24 = 28
15. Protons = 16, mass = 32: Sulfur (S), neutrons = 16
16. Gold: atomic number = 79, mass = 197 → neutrons = 197 - 79 = 118
17. Atomic number = 76, neutrons = 114: Osmium (Os), mass = 76 + 114 = 190

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Completed Table

| Element Name | Atomic Number | Number of Protons | Number of Neutrons | Mass Number |
|--------------|----------------|--------------------|---------------------|-------------|
| carbon | 6 | 6 | 6 | 12 |
| oxygen | 8 | 8 | 8 | 16 |
| hydrogen | 1 | 1 | 0 | 1 |
| helium | 2 | 2 | 2 | 4 |
| hydrogen | 1 | 1 | 2 | 3 |
| nitrogen | 7 | 7 | 7 | 14 |
| hydrogen | 1 | 1 | 1 | 2 |
| uranium | 92 | 92 | 146 | 238 |
| potassium | 19 | 19 | 20 | 39 |
| sodium | 11 | 11 | 12 | 23 |
| silver | 47 | 47 | 61 | 108 |
| xenon | 54 | 54 | 77 | 131 |
| bromine | 35 | 35 | 45 | 80 |
| chromium | 24 | 24 | 28 | 52 |
| sulfur | 16 | 16 | 16 | 32 |
| gold | 79 | 79 | 118 | 197 |
| osmium | 76 | 76 | 114 | 190 |

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Answering the Questions

#### 1. How are the atomic number and the number of protons related to each other?

The atomic number is equal to the number of protons in the nucleus. This defines the element.

> ✔ Answer: The atomic number is the same as the number of protons.

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#### 2. How do the number of protons, number of neutrons, and the mass number relate to each other?

$$
\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}
$$

> ✔ Answer: The mass number is the sum of protons and neutrons.

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#### 3. What is the one thing that determines the identity of an atom?

The number of protons (i.e., the atomic number) determines the identity of an atom.

> ✔ Answer: The number of protons (atomic number).

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#### 4. What subatomic parts are equal to make a neutral atom?

In a neutral atom, the number of protons equals the number of electrons.

> ✔ Answer: Number of protons = Number of electrons.

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#### 5. Explain in your words how to calculate the mass of a sodium atom.

To calculate the mass of a sodium atom:
- Look up its atomic number (11) → number of protons = 11
- Find the most common isotope’s mass number (usually 23 for sodium)
- Add protons and neutrons: 11 protons + 12 neutrons = 23
- The mass number (23) is approximately the atomic mass in atomic mass units (amu)

> ✔ Answer: The mass of a sodium atom is calculated by adding the number of protons (11) and neutrons (12), giving a mass number of 23 amu.

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#### 6. Draw and label three element symbols that are representative of the periodic table. It should have atomic #, mass #, name and element symbol.

Since I can't draw here, I’ll describe how to draw them.

Each symbol looks like:

```
Mass Number
A
Z X
(name)
```

Where:
- Z = atomic number
- X = chemical symbol
- A = mass number
- Name = full name

Example 1: Carbon
```
12
C
6
Carbon
```

Example 2: Oxygen
```
16
O
8
Oxygen
```

Example 3: Sodium
```
23
Na
11
Sodium
```

> ✔ You can draw these in your notebook with proper formatting.

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✔ Final Summary

- The chart is now complete.
- All questions are answered clearly.
- Use the knowledge of atomic structure to fill in blanks using:
- Atomic number = protons
- Mass number = protons + neutrons
- Element identity = number of protons
- Neutral atom → protons = electrons

Let me know if you'd like this formatted as a printable PDF or need help drawing the symbols!