WATCH ALL SLIDES

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.

Slide 12

Is the nucleus the largest part of an atom?

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

Slide 13

Modeling an Atom

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

Slide 14

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

Slide 15

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.

Slide 16

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.

Slide 17

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.

Slide 18

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.

Slide 19

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

Slide 20

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.

Slide 21

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