4. Back to the beginning page 12
Photo of discharge tube
Picture 4.1 A discharge tube. Atoms are broken up by fast moving electrons.
Fundamentally right
We can remove electrons from atoms in a discharge tube. The tube contains a gas such as neon and it has two electrical connections. A high voltage is put across the connections and a current of electrons passes through the gas inside. These electrons bump into the atoms of the gas and knock off their electrons.

The fact that we can knock electrons off the atoms shows that atoms are not fundamental - they must be made of electrons and something else (protons and neutrons).

So are the electrons, protons and neutrons fundamental particles, or can we break them into smaller pieces?

Fundamental particles
Electrons are fundamental particles and, as far as we know, cannot be made simpler. The electron is a member of the lepton family of fundamental particles.

Protons and neutrons are not fundamental and can be broken down into smaller, fundamental parts. Each proton and neutron contains 3 quarks.

Quarks and leptons are fundamental particles. They were the first particles to be born soon after the Big Bang.

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Question 11
Look at the particles below.
a) Which of the particles are fundamental?
b) Which one particle is the simplest particle found inside the nucleus?
particle a) fundamental b) simplest in