Atoms, Molecules, and Compounds

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Part 1: Guided Notes

Atom: The smallest unit of an element that still has the properties of that element.

Element: A substance made of only one type of atom.

Molecule: Two or more atoms that are chemically bonded together.

Molecular compound: A molecule made from atoms of two or more different elements.

Particle-model key: Colored circles are models of atoms. They are not photographs of real atoms.

Red = Element R Blue = Element B Green = Element G

1. Complete the quick checks.

How many elements are shown in two joined red circles? ________

Are the atoms bonded? ______________________________

How many elements are shown in one blue circle joined to one green circle? ________

Are the atoms bonded? ______________________________

Word bank: atom molecule one two or more bonded not bonded element molecular compound

Sentence frame: This model is a __________________ because it has __________ atoms from __________ different element(s).

Part 2: Partner Modeling Task

Use modeling clay or linking spheres. Take turns as the Builder and Science Recorder. Switch roles after Model 2. Sketch each model and complete the comparison record.

1. Build one red sphere. This represents one atom of Element R. Sketch it below.

2. Join two red spheres. This represents a molecule made from one element. Sketch it below.

3. Join one red sphere to two white spheres. This represents a molecular compound made from different elements. Sketch it below.

4. Place two spheres next to each other without joining them. This is not one molecule. Sketch it below.

Partner check: For each model, ask: How many atoms? How many elements? Are the atoms bonded?

Model 1: one atom
Number of atoms: ______ Number of elements: ______
Bonded or not bonded: __________________
Classification: __________________________

Model 2: two joined red atoms
Number of atoms: ______ Number of elements: ______
Bonded or not bonded: __________________
Classification: __________________________

Model 3: one red joined to two white
Number of atoms: ______ Number of elements: ______
Bonded or not bonded: __________________
Classification: __________________________

Model 4: two separate particles
Number of atoms: ______ Number of elements: ______
Bonded or not bonded: __________________
Classification: __________________________

Explain: Why is Model 3 a molecular compound?

Part 3: Individual Exit Ticket

1. Define molecule in your own words.

2. The diagram shows two blue atoms joined to one green atom: 🔵—🔵—🟢

Classify the diagram. Use evidence about the number of atoms, the number of elements, and whether the atoms are bonded.

Sentence frame: This is a __________________ because it contains ______ atoms from ______ different elements, and the atoms are __________________.

3. Draw a molecule made from only one element. Use the particle-model key and show the atoms joined together.