Radioactivity and Nuclear Reactions

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Protons and neutrons are packed together tightly so that the nucleus takes up only a tiny part of an atom.

If an atom were the size of a football stadium, its nucleus would be the size of a marble!

Despite taking little space, the nucleus contains almost all the mass of the atom.

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Is the nucleus the largest part of an atom?

A proton or neutron has about 2,000 times the mass of an electron.

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Modeling an Atom

To create a model or drawing of an atom visit this site: education.jlab.org/qa/atom_model.html

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The Strong Force

The force that makes protons and neutrons attract each other and stay together.

100 times stronger than the electric force

Only works when particles are close

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How do forces work in a small nucleus?

In a small nucleus, the particles are close together so that the strong force holds the protons and neutrons tightly together.

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How do forces work in a large nucleus?

In a large nucleus, the strong force holds together only the particles that are closest to one another.

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How do forces work in a large nucleus?

In a large nucleus, the strong force holds together only the particles that are closest to one another.

In a nucleus with many protons, the electric force repels protons that are far apart.

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How do forces work in a large nucleus?

In a large nucleus, the strong force holds together only the particles that are closest to one another.

In a nucleus with many protons, the electric force repels protons that are far apart.

This increased repulsive force causes the particles in a large nucleus to be held less tightly than those in a small nucleus.

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Radioactivity

When the strong force can hold a nucleus together forever, the nucleus is stable.

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Radioactivity

When the strong force can hold a nucleus together forever, the nucleus is stable.

If not, the nucleus becomes unstable and can break apart or decay by emitting particles and energy.

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