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Lesson · Grade 8 · Science

Inside the nucleus: protons, neutrons and quarks

  • Grade 8
  • Science
  • 1 min 51 s
  • British Columbia
  • BC8-SC-26

The video zooms in from a helium atom to its nucleus, then to one proton and one neutron, showing that a proton is two up quarks and one down quark and a neutron is one up quark and two down quarks. Adding the quark charges (+2/3 and −1/3) gives +1 for the proton and 0 for the neutron, and the strong force holds the quarks so tightly that they are never found alone, so protons and neutrons are not the smallest pieces of matter.

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In one sentence

The question this lesson answers

Many people think protons and neutrons are the smallest pieces of matter. Are they?

Here is a helium atom. Two tiny electrons move around its centre, called the nucleus.

Transcript

What the lesson says

Many people think protons and neutrons are the smallest pieces of matter. Are they?

Here is a helium atom. Two tiny electrons move around its centre, called the nucleus.

Zoom in on the nucleus. In this atom, it holds two protons and two neutrons, packed tightly together.

Now zoom in again, on one proton and one neutron.

A proton has an electric charge of plus one. A neutron has no charge, so its charge is zero.

Inside each one are even smaller particles called quarks.

A proton is made of two up quarks and one down quark. Up and down are just the names of two kinds of quark.

An up quark has a charge of plus two thirds. A down quark has a charge of minus one third.

For the proton: plus two thirds, plus two thirds, minus one third. That makes plus one.

A neutron is made of one up quark and two down quarks.

For the neutron: plus two thirds, minus one third, minus one third. That makes zero.

These totals match the charges: plus one for a proton and zero for a neutron.

A force called the strong force holds quarks together, so tightly that a quark is never found on its own.

So protons and neutrons are not the smallest pieces of matter. They are made of quarks.

Recap: the protons and neutrons in the nucleus are each made of three quarks.

Curriculum

Where this fits

British Columbia, Grade 8

Science, Physics: protons, neutrons, and quarksBC8-SC-26

Next: The Strong Nuclear Force: What Holds the Nucleus Together

The outcomes and strands follow the British Columbia curriculum.

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