SOLUTION: Atomic mass and atomic number worksheet key - Studypool - Free Printable

Let's solve each question step by step.

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Q.6: What is the particle in a nucleus that determines the identity of the element?

Answer:
c) Proton

Explanation:
The atomic number of an element is defined as the number of protons in the nucleus of an atom. Each element has a unique number of protons. For example, all atoms with 6 protons are carbon atoms, regardless of the number of neutrons or electrons. Therefore, the proton determines the identity of the element.

- Electrons (b) can vary in number (forming ions), so they don't define the element.
- Neutrons (d) can vary (isotopes), so they don’t determine the element’s identity.
- Mass number (a) is the sum of protons and neutrons and varies between isotopes.

✔ So, the correct answer is c) Proton.

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Q.7: The number of ____________ can be calculated by subtracting its atomic number from its mass number.

Answer:
d) neutrons

Explanation:
The mass number = number of protons + number of neutrons
The atomic number = number of protons

So,
Number of neutrons = Mass number – Atomic number

For example:
- Oxygen-16: mass number = 16, atomic number = 8 → neutrons = 16 - 8 = 8

✔ So, the correct answer is d) neutrons

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Q.8: Complete the following chart

We’ll fill in the table using the information provided:

| Symbol | Element | Atomic Number | Number of Protons | Number of Neutrons | Mass Number |
|--------|---------|----------------|--------------------|---------------------|-------------|
| $^{17}_{8}\text{O}$ | Oxygen | 8 | 8 | ? | 17 |
| $^{18}_{8}\text{O}$ | Oxygen | 8 | 8 | ? | 18 |
| $^{63}_{27}\text{Co}$ | Cobalt | 27 | 27 | ? | 63 |
| $^{222}_{88}\text{Ra}$ | Radon | 88 | 88 | ? | 222 |
| $^{226}_{88}\text{Ra}$ | Radium | 88 | 88 | ? | 226 |

Now calculate number of neutrons = Mass number – Atomic number

#### Row 1: $^{17}_{8}\text{O}$
- Element: Oxygen
- Atomic Number: 8
- Protons: 8
- Neutrons: 17 – 8 = 9
- Mass Number: 17

#### Row 2: $^{18}_{8}\text{O}$
- Element: Oxygen
- Atomic Number: 8
- Protons: 8
- Neutrons: 18 – 8 = 10
- Mass Number: 18

#### Row 3: $^{63}_{27}\text{Co}$
- Element: Cobalt
- Atomic Number: 27
- Protons: 27
- Neutrons: 63 – 27 = 36
- Mass Number: 63

#### Row 4: $^{222}_{88}\text{Ra}$
- Element: Radon (Note: Ra is Radium, but symbol Ra corresponds to Radium)
Wait — correction:

Actually:
- $^{222}_{88}\text{Ra}$: Radium, not Radon.
- Radon is Rn, atomic number 86.
- Radium (Ra) has atomic number 88.

So:
- Element: Radium
- Atomic Number: 88
- Protons: 88
- Neutrons: 222 – 88 = 134
- Mass Number: 222

#### Row 5: $^{226}_{88}\text{Ra}$
- Element: Radium
- Atomic Number: 88
- Protons: 88
- Neutrons: 226 – 88 = 138
- Mass Number: 226

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✔ Final Completed Chart:

| Symbol | Element | Atomic Number | Number of Protons | Number of Neutrons | Mass Number |
|--------|-----------|---------------|--------------------|---------------------|-------------|
| $^{17}_{8}\text{O}$ | Oxygen | 8 | 8 | 9 | 17 |
| $^{18}_{8}\text{O}$ | Oxygen | 8 | 8 | 10 | 18 |
| $^{63}_{27}\text{Co}$ | Cobalt | 27 | 27 | 36 | 63 |
| $^{222}_{88}\text{Ra}$ | Radium | 88 | 88 | 134 | 222 |
| $^{226}_{88}\text{Ra}$ | Radium | 88 | 88 | 138 | 226 |

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Summary of Answers:

- Q.6: c) Proton
- Q.7: d) neutrons
- Q.8: Table completed as above.

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