Keshu

What are atoms like

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Atoms are made up of three kinds of particles: protons, neutrons, electrons.

These particles are arranged in a similar way in every atom

The protons and neutrons are tightly packed in the center. There they form the nucleus of the atom.

The electrons orbit the nucleus around it.

The three different particles in a atom have different properties.

Protons and neutrons have much more mass than electrons.

electrons almost have no mass at all.

Protons have a positive electric charge.

Neutrons have no electric charge (neutral).

Electrons have a negative charge.

There is a lot of empty space between the parts of an atom. This space between the parts of an atom. This space really is completely empty -- there is nothing in it at all.

How did scientists come up with this model of an atom

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Scientists from different parts of the world have worked on a number of different ideas that have led to the model of the atom which we see today.

In the late 1890s a British scientist called J.J. Thompson discovered the electron. His model for the atom was that the different parts of the atom were scattered throughout the structure.

One of Thompson's research students originally came from New Zealand. His name was Ernest Rutherford. Rutherford discovered the proton in 1909 and the nucleus in 1911. Rutherford's most famous experiment was the gold foil experiment.

In this experiment Rutherford fired fast- moving particles smaller than an atom at a very thin gold foil. Most of the particles passed straight through the foil. Only a few of these particles (about 1 in 20,000) were deflected in various directions. This led Rutherford to have the idea that gold atoms must be mostly empty space, with there particles packed into a dense nucleus at the center. This helped to move towards the model of the atom we use today.

James Chadwick worked with Rutherford and Thompson. In 1932, he proved that neutrons exist.