# Atoms, Isotopes, and Particles

Part of the Nuclear Science Merit Badge Digital Resource Guide: [Introduction & Overview](https://merit-badge.university/merit-badges/nuclear-science/guide/index.md)

*2. Atomic Building Blocks*

> **2.** Do the following:

This requirement gives you the vocabulary and models that make the rest of the badge easier to understand. First you learn the parts of matter and the language scientists use. Then you turn those ideas into something you can build and explain with your own hands.

## Requirement 2a

> **2a.** Explain the following terms: atom, nucleus, proton, neutron, electron, quark, isotope; alpha particle, beta particle, gamma ray, X-ray; ionization, radioactivity, radioisotope, and stability.

A strong explanation connects the terms instead of listing them like flash cards.

An **atom** is the basic unit of an element. At its center is the **nucleus**, made of **protons** and **neutrons**. **Electrons** move around the nucleus in the surrounding electron cloud. Protons and neutrons are built from smaller particles called **quarks**.

An **isotope** is a version of the same element that has the same number of protons but a different number of neutrons. Some isotopes are stable. Some are unstable and change over time.

When an unstable nucleus changes and gives off energy or particles, that is **radioactivity**. A radioactive isotope is a **radioisotope**.

The main emissions you need to know are:

| Term | What it is | What to remember |
| --- | --- | --- |
| Alpha particle | 2 protons + 2 neutrons | heavy, charged, stopped easily |
| Beta particle | fast electron or positron | lighter, travels farther than alpha |
| Gamma ray | high-energy electromagnetic radiation | no mass, very penetrating |
| X-ray | high-energy electromagnetic radiation usually produced outside the nucleus | also penetrating, often made by equipment |

**Ionization** happens when enough energy knocks electrons off atoms. **Stability** describes whether a nucleus tends to stay the same or decay.

> **Tip**
>
> If you are explaining these terms to your counselor, build from the inside out: nucleus first, then electrons, then isotopes, then radiation types, then what makes an atom stable or unstable.

[Glossary of Nuclear Science Terms (website)](https://nplab.webspace.durham.ac.uk/glossary/): A plain-language glossary you can use to check your definitions and make sure you are using each term correctly.

Video: [What Are Isotopes? (video)](https://youtu.be/faB9Gb7bl9I?si=Et7Yi1cp8zLvyppP)

Video: [Quarks Explained (video)](https://youtu.be/LraNu_78sCw?si=o4zrlNUwhUT69eB6)

## Requirement 2b

> **2b.** Choose an element from the periodic table. Construct 3-D models for the atoms of three isotopes of this element, showing neutrons, protons, and electrons. Write down the isotope notation for each model including the atomic and mass numbers. In a separate model or diagram, explain or show how quarks make up protons and neutrons.

This is where the badge stops being only words and turns into a model you can point to. Pick an element with several common isotopes so the pattern is easy to see. Hydrogen, carbon, oxygen, and chlorine all work well.

### How to choose your element

Look for an element where the **atomic number** stays the same but the **mass number** can change. The atomic number tells you how many protons the element always has. The mass number is protons plus neutrons. Change the neutrons, and you have a new isotope of the same element.

### What your three models should show

**What to label on each isotope model** — Make the differences easy to see

- [ ] **Protons**: these identify the element.
- [ ] **Neutrons**: these are what make one isotope different from another.
- [ ] **Electrons**: for a neutral atom, these match the proton count.
- [ ] **Atomic number**: the proton count.
- [ ] **Mass number**: protons plus neutrons.
- [ ] **Isotope notation**: for example, carbon-12 or \(^12_6\text{C}\).

A good set of models does not need to be fancy. Colored clay, beads, paper circles, or a digital drawing can all work if the structure is clear.

### Showing quarks

In your separate model or diagram, show that:

- a **proton** is made of two up quarks and one down quark
- a **neutron** is made of one up quark and two down quarks

You do not need to explain every detail of particle physics. The goal is to show that protons and neutrons are not indivisible. They are made from smaller parts.

> **Did You Know?**
>
> Two atoms of carbon can behave almost identically in chemistry while having different numbers of neutrons. That small change is enough to create different isotopes with different nuclear behavior.

[Make a Model of an Isotope (PDF)](https://filestore.scouting.org/filestore/Merit_Badge_ReqandRes/Requirement%20Resources/Nuclear%20Science/Isotope%20Model%20Activity.pdf): A step-by-step activity sheet that can help you organize your isotope models and notation.

[Interactive Isotopes (website)](https://isotopes.ans.org/): Lets you explore real isotope data and compare proton, neutron, and mass-number patterns before you build your model.

![Three side-by-side isotope models of the same element with protons, neutrons, electrons, and isotope notation labeled](https://ik.imagekit.io/doulacoop/tr:w-800/mbu-assets/merit-badges/nuclear-science/guide/isotope-model-example?v=5601e105)

Once you are comfortable with atoms and isotopes, you are ready to look at machines that hurl particles at incredible speeds to learn even more.

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- Previous: [Understanding Radiation](https://merit-badge.university/merit-badges/nuclear-science/guide/req1/index.md)
- Next: [How Accelerators Work](https://merit-badge.university/merit-badges/nuclear-science/guide/req3a/index.md)