๐Ÿงช Chemistry Lab
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DEVELOPMENT OF THE ATOMIC MODEL

How our idea of the atom changed

1803 โ€ข John Dalton

Solid Sphere Model

Matter is made of tiny particles called atoms.

Portrait of John Dalton
John Dalton Proposed the Solid Sphere Model
HOW THIS MODEL DEVELOPED

Dalton developed one of the first modern scientific atomic theories to explain how elements combine.

KEY IDEA

Elements are made from characteristic atoms that combine in simple whole-number ratios.

ATOM SCALE
Click the model to continue
EXPERIMENT: THE CATHODE RAY

What did J. J. Thomson observe?

Change the gas and electrode metals, then move the magnet along the tube. Watch what happens to the cathode ray.

N S
โ†” Drag the magnet along the outside of the tube

Gas glow colours are simplified visual cues rather than representations of complete emission spectra.

J. J. Thomson's experiment Watch the experiment, then return to the simulation.
EXPERIMENT: GOLD FOIL SCATTERING

What happened when alpha particles hit gold foil?

Fire alpha particles towards a very thin sheet of gold. Watch how most pass through while a small number are deflected.

Particle paths and frequencies are simplified for teaching and are not drawn to scale.

NEXT: THE PERIODIC TABLE

Where do the elements belong?

Elements are arranged into vertical columns called groups. Put the missing groups back into the simplified periodic table.

Missing groups

Drag a group into the table, or click a group and then click where it belongs.

Place group
Place group
Transition metals begin here after calcium
Place groups
Place group
Place group
0 / 5 groups placed

Choose a group to begin.

Explore the chemistry syllabus โ†“
CHEMISTRY CONTENTS

What would you like to learn?

Choose a chapter to see its topics and available interactive activities.

FORM 4
FORM 5