All About The Atom Notes: How to Find the Subatomic Particles ... - Free Printable

Let's solve the worksheet step by step and fill in all the missing information.

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Part 1: Fill in the missing information for an atom of Helium

We are given a diagram of a helium atom with three colored particles:

- Yellow circle with a minus sign (–) → This represents an electron.
- Red circle with a plus sign (+) → This represents a proton.
- Green circle (no charge shown) → This represents a neutron.

So, the answers are:

- 🔴 Yellow (–) = Electron
- 🔴 Red (+) = Proton
- 🟢 Green = Neutron

> 💡 Note: In the diagram of the helium atom:
> - The nucleus has 2 protons (red) and 2 neutrons (green).
> - There are 2 electrons (yellow) orbiting around the nucleus.

This matches helium’s atomic structure:
- Atomic number = 2 → 2 protons
- Mass number ≈ 4 → 2 protons + 2 neutrons
- 2 electrons to balance charge

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Part 2: Reading the Periodic Table – Oxygen Example

We’re given the periodic table box for Oxygen (O):

```
8
O
Oxygen
15.999
```

Now let’s label each part using the arrows.

#### Atomic Number:
- Arrow pointing to 8
- Definition: The atomic number is the number of protons in the nucleus.
- It also tells us the number of electrons in a neutral atom.

✔ So, fill in:
- Atomic number: The top-left number.
- It is the number of protons in an atom.
- It also tells us the number of electrons.

#### Atomic Mass:
- Arrow pointing to 15.999
- This is the atomic mass, found at the bottom of the box.
- It is the average mass of the atom (in atomic mass units).
- It is the total number of protons PLUS neutrons in the nucleus.

✔ So, fill in:
- Atomic mass: The number at the bottom.
- It is the average mass of the atom.
- It is the number of protons PLUS (+) the number of neutrons in the nucleus.

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✔ Final Completed Answers:

#### Subatomic Particles (Helium Atom):
- Yellow (–) = Electron
- Red (+) = Proton
- Green = Neutron

#### Reading the Periodic Table:

Atomic number:
- The top-left number.
- It is the number of protons in an atom.
- It also tells us the number of electrons.

Atomic mass:
- The number at the bottom.
- It is the average mass of the atom.
- It is the number of protons PLUS (+) the number of neutrons in the nucleus.

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🧠 Summary:

- Atomic number = number of protons = number of electrons (in neutral atoms)
- Atomic mass ≈ protons + neutrons (electrons have negligible mass)
- For oxygen:
- Atomic number = 8 → 8 protons, 8 electrons
- Atomic mass ≈ 16 → so ~8 neutrons (16 – 8 = 8)

Let me know if you'd like this turned into a printable version or need help with more elements!