Exploring atoms: atom structure

Exploring atoms

Atom structure

Everything in the universe is made up of atoms. But what are atoms made of? Are they made of even smaller parts?

Scientists working on atoms faced a challenge how could they discover the structure of something so tiny?

We're going to investigate the structure of atoms, along with how scientists developed models of the atom.

Models of the atom

Probing the atom with α-particles

Select the emitter to fire a particle at the sphere. Then choose the correct statement.

In 1909, the physicist Ernest Rutherford had the idea of using positively charged α-particles (alpha particles) to investigate the structure of atoms.

Let's find out how a small, positively charged particle behaves when it is fired at a heavy, positively charged sphere.

Ernest Rutherford in his laboratory at McGill University, Montreal, in 1905.

Select the image to find out more.

Ernest Rutherford 1871-1937

Ernest Rutherford was born in New Zealand in 1871. At the age of 24, he moved to England to study science at Cambridge.

Soon afterwards, his professor JJ Thomson discovered the electron and proposed a model of the atom. Rutherford made his own discoveries on radioactive substances.

By 1907, Rutherford had become a professor himself. As the result of his work and the experiments of two of his students, he developed a new model of the atom, which changed the way we think about the atom today.

In 1908, Rutherford was awarded the Nobel Prize in Chemistry for his work on radioactive particles. He was one of the most honoured scientists of his time.

Positive α-particle emitter

When a small positive particle is fired at a positively charged sphere, the positive particle:

hits the positive sphere

swerves away from the positive sphere

swerves toward the positive sphere.

right & wrong here

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Acknowledgements

Please refer to Conditions of use.

Ernest Rutherford in his laboratory at McGill University, Montreal, in 1905. CC BY 4.0

Rutherford's experiment

This is a model of Rutherford's experiment. He set two students, Geiger and Marsden, the task of firing α-particles at a thin sheet of gold foil.

Special equipment was required to detect how the particles were deflected through different angles by the gold atoms.

The results were surprising, because the particle paths didn't fit the model of the atom accepted by most scientists at the time. The experiment helped Rutherford establish a new model of the atom.

Select On to try it.

Microscope

Movable fluorescent screen

Scintillation

radioactive source

lead shield

gold foil

lead screen with slit

beam of α-particles

Using particle paths to understand atom structure

For each particle path diagram, choose the atom model that most closely matches it.

Find the structure of the atom

Sample text..

Atom models

α-particle emitter

Gold atom

A new model

Good work!

Like Ernest Rutherford, you've built a picture of what is inside atoms.

Before this experiment, most scientists accepted the plum pudding model of the atom. But Rutherford showed that most of the mass of an atom must be concentrated in a tiny, positively charged nucleus. Light, negative electrons occupy the rest of the space. This is true of all atoms.

The diameter of a nucleus is less than
1/10 000 the diameter of an atom, and electrons are far tinier still.

If this atom diagram were drawn to scale, both the nucleus and the electrons would be too small to see.

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