Educational worksheet on basic atomic structure covering nucleus, electrons, protons, neutrons, atomic mass, and isotope calculations.

Let's go through the Basic Atomic Structure Worksheet step by step and fill in the correct answers with explanations.

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1. The central part of the atom is called the ________

✔ Answer: Nucleus

🔹 *Explanation:* The nucleus is the dense, central core of an atom that contains protons and neutrons.

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2. Electrons are found ________ the nucleus.

✔ Answer: around / outside / surrounding

🔹 *Explanation:* Electrons orbit the nucleus in energy levels or shells, so they are located outside the nucleus.

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3. The nucleus has a ________ charge and contains ________ and ________.

✔ Answer: positive, protons, neutrons

🔹 *Explanation:* Protons have a positive charge, neutrons are neutral, so the nucleus overall has a positive charge due to protons.

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4. The ________ and the ________ have the same mass.

✔ Answer: Proton, Neutron

🔹 *Explanation:* Protons and neutrons each have approximately the same mass (~1 atomic mass unit), while electrons are much lighter.

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5. Give the charge of each:

- Proton: +1
- Neutron: 0 (neutral)
- Electron: -1

✔ Answer:
- Proton: +1
- Neutron: 0
- Electron: -1

🔹 *Explanation:* These are fundamental charges:
- Proton = +1 elementary charge
- Neutron = no charge (neutral)
- Electron = -1 elementary charge

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6. Order from the lightest to heaviest: Protons, Electrons, Nucleus, Neutrons

✔ Answer: Electrons < Protons ≈ Neutrons < Nucleus

🔹 *Explanation:*
- Electrons are much lighter than protons or neutrons.
- Protons and neutrons have nearly equal masses (~1 amu).
- The nucleus is the sum of all protons and neutrons, so it's the heaviest.

So the order is:
Electrons → Protons → Neutrons → Nucleus
(Note: Protons and neutrons have almost identical mass, so they can be grouped together.)

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7. The ________ of an element is the average mass of an element’s naturally occurring atoms, or isotopes, taking into account the ____ of each isotope.

✔ Answer: Atomic mass, abundance

🔹 *Explanation:* The atomic mass (or average atomic mass) is a weighted average based on the relative abundance of each isotope.

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8. The ________ of an element is the total number of protons and neutrons in the ________ of the atom.

✔ Answer: Mass number, nucleus

🔹 *Explanation:* The mass number = protons + neutrons, and both are located in the nucleus.

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9. 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 ________ from the ________.

✔ Answer: neutrons, atomic number, mass number

🔹 *Explanation:*
To find the number of neutrons:
👉 Number of neutrons = Mass number – Atomic number

- Atomic number = number of protons
- Mass number = protons + neutrons

So:
Neutrons = Mass number – Atomic number

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10. Answer the following questions about the $^{20}\text{Ne}_{10}$ atom:

This notation means:
- Mass number (A) = 20
- Atomic number (Z) = 10
- Element is Neon (Ne)

#### a) No. of protons
✔ Answer: 10
🔹 *Explanation:* Atomic number = number of protons = 10

#### b) No. of neutrons
✔ Answer: 10
🔹 *Explanation:* Neutrons = Mass number – Atomic number = 20 – 10 = 10

#### c) No. of electrons
✔ Answer: 10
🔹 *Explanation:* In a neutral atom, number of electrons = number of protons = 10

#### d) Mass number
✔ Answer: 20
🔹 *Explanation:* Given directly in the superscript.

#### e) Atomic number
✔ Answer: 10
🔹 *Explanation:* Given in the subscript.

#### f) No. of valence electrons
✔ Answer: 8
🔹 *Explanation:* Neon is in Group 18 (Noble gases), and has a full outer shell. Its electron configuration is:
1s² 2s² 2p⁶ → 2,8
So, 8 valence electrons (in the second shell).

> ✔ Note: Valence electrons are the electrons in the outermost shell. For neon, the outer shell (n=2) has 8 electrons.

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✔ Final Answers Summary:

| Question | Answer |
|--------|--------|
| 1 | Nucleus |
| 2 | around / outside |
| 3 | positive, protons, neutrons |
| 4 | proton, neutron |
| 5 | Proton: +1, Neutron: 0, Electron: -1 |
| 6 | Electrons < Protons ≈ Neutrons < Nucleus |
| 7 | Atomic mass, abundance |
| 8 | Mass number, nucleus |
| 9 | neutrons, atomic number, mass number |
| 10a | 10 |
| 10b | 10 |
| 10c | 10 |
| 10d | 20 |
| 10e | 10 |
| 10f | 8 |

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