Atomic Structure Worksheet | Exams Chemistry | Docsity - Free Printable

Let's go through the Atomic Structure Worksheet and verify each answer, explain the reasoning, and correct any errors if needed.

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Diagram Labeling (1–3)

The diagram shows a simplified atom with:

- A central nucleus containing protons (+) and neutrons (no charge).
- Electrons (-) orbiting in shells.

Based on standard labeling:

1. Nucleus – The central part of the atom containing protons and neutrons.
2. Proton – The positively charged particle in the nucleus.
3. Electron – The negatively charged particle orbiting the nucleus.

✔ So:
- 1: Nucleus
- 2: Proton
- 3: Electron

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Questions & Answers

#### 4. What type of charge does a proton have?
- ✔ Answer: + (Positive)
- Protons carry a positive charge.

#### 5. What type of charge does a neutron have?
- ✔ Answer: neutral
- Neutrons have no charge; they are neutral.

#### 6. What type of charge does an electron have?
- ✔ Answer: – (Negative)
- Electrons carry a negative charge.

#### 7. Which two subatomic particles are located in the nucleus of an atom?
- ✔ Answer: p + n (protons and neutrons)
- The nucleus contains protons and neutrons.

#### 8. What is the charge of an atom?
- ✔ Answer: neutral
- In a neutral atom, the number of protons (+) equals the number of electrons (–), so net charge = 0.

#### 9. What is the charge of an ion? (Explain your answer fully.)
- ✔ Answer: + or –, because ions gain or lose electrons.
- Ions are charged atoms. If an atom loses electrons → becomes positive ion (cation).
If it gains electrons → becomes negative ion (anion).

#### 10. If an atom has 35 protons in the nucleus, how many electrons will it have orbiting the nucleus?
- ✔ Answer: 35
- In a neutral atom, number of electrons = number of protons.

#### 11. What is the atomic number of the atom in the diagram above?
- 🔍 Let's analyze the diagram:
- There are 5 protons shown in the nucleus (marked with +).
- Atomic number = number of protons.
- ✔ Answer: 5 ✔️ Correct.

#### 12. What is the atomic mass/mass number of the atom in the diagram above?
- 🔍 Mass number = protons + neutrons
- Protons: 5
- Neutrons: Count the uncharged circles in the nucleus → there are 6 neutrons.
- So, mass number = 5 + 6 = 11
- ✔ Answer: 11 ✔️ Correct.

#### 13. How many protons are in the nucleus of an atom with an atomic number of 15?
- Atomic number = number of protons
- ✔ Answer: 15 ✔️ Correct.

#### 14. How many electrons are in the nucleus of an atom with an atomic number of 20?
- ✘ This question is tricky — electrons are not in the nucleus.
- Electrons orbit outside the nucleus.
- Even though the atom has 20 protons (and thus 20 electrons in neutral state), none are in the nucleus.
- ✔ Correct answer: 0
- But the student wrote 20 → ✘ Incorrect.

> ⚠️ Correction: Electrons are not in the nucleus. The nucleus only contains protons and neutrons.

#### 15. How many neutrons are in the nucleus of an atom with an atomic number of 25? (use Periodic Table for mass)
- Atomic number = 25 → element is Manganese (Mn)
- From periodic table: Atomic mass ≈ 55
- Number of neutrons = mass number – atomic number = 55 – 25 = 30
- ✔ Answer should be: 30
- Student didn’t write anything → ✘ Missing.

#### 16. What is the mass number of an atom with 3 protons, 4 neutrons, and 3 electrons?
- Mass number = protons + neutrons = 3 + 4 = 7
- Electrons don’t contribute to mass number.
- ✔ Answer: 7 ✔️ Correct.

#### 17. How many neutrons are in the nucleus of an atom that has an atomic mass of 36 and an atomic number of 25?
- Neutrons = mass number – atomic number = 36 – 25 = 11
- ✔ Answer: 11 ✔️ Correct.

#### 18. The atomic number tells you the number of ________ in one atom of an element. It also tells you the number of ________ in a neutral atom of that element. The atomic number gives the "identity" of an element as well as its location on the Periodic Table. No two different elements will have the same atomic number.

- First blank: protons
- Second blank: electrons (in a neutral atom)
- Third blank: same
- ✔ All answers correct: protons, electrons, same ✔️

#### 19. The mass number is used to calculate the number of ________ in one atom of an element. In order to calculate the number of neutrons you must subtract the # p from the mass #.

- First blank: neutrons
- Second blank: # p (number of protons)
- Third blank: mass #
- ✔ Student wrote: p, n, e ? → ✘ Incorrect.
- The mass number helps find neutrons, not protons, neutrons, and electrons all together.

> ✔ Correct answer:
> "The mass number is used to calculate the number of neutrons in one atom of an element. In order to calculate the number of neutrons you must subtract the # p (atomic #) from the mass #."

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✔ Final Summary of Corrections:

| Question | Student Answer | Correct Answer | Notes |
|--------|----------------|----------------|-------|
| 14 | 20 | 0 | Electrons are NOT in the nucleus |
| 15 | (blank) | 30 | Mn has mass ~55, 55 - 25 = 30 neutrons |
| 19 | p, n, e? | neutrons, # p, mass # | Only neutrons are calculated using mass number |

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✔ Fully Corrected Worksheet Answers:

1. Nucleus
2. Proton
3. Electron

4. +
5. neutral
6. –
7. protons and neutrons (p + n)
8. neutral
9. + or –, because ions gain or lose electrons
10. 35
11. 5
12. 11
13. 15
14. 0 ← CORRECTED
15. 30 ← CORRECTED
16. 7
17. 11
18. protons, electrons, same
19. neutrons, # p (atomic #), mass # ← CORRECTED

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