Fundamental Particles

You'll no doubt be familiar with the basic structure of atoms by now, with negative electrons orbitting a positive nucleus. - But what makes up these structures?

• What are electrons made from? [1]

  • Electrons are fundamental particles - meaning you can't divide electrons into even smaller particles

• What charge does an electron carry? [1]

  • Electrons have an electrically negative charge. 
    • Are electrons and protons approximately the same size? [1]
      • No! Although a proton has an electrically positive charge, a proton is much larger than an electron and is not a fundamental particle like an electron.
      • Is there a fundamental particle that is approximately the same size as an electron, but positive? [1]
        • Yes! The electron's positive equivalent is called the "positron"

• A positron is the anti-particle of an electron.  What is an anti-particle? [1]

  • Every particle has an antiparticle. An antiparticle (e.g. a positron) has the same mass but opposite charge of its 'normal' particle (e.g. an electron).
    • Where do anti-particles come from? [1]
      • When two particles collide at very high speed, they release lots of energy. This energy can turn into mass. The created mass comes in equal amounts of matter and antimatter (Antimatter is made of antiparticles).

• What are protons and neutrons made from? [2]

  • Protons and Neutrons are NOT fundamental particles - they're made up of even smaler particles called "quarks".
  • How many different types of quarks are protons and neutrons made from? [2]
    • There are various types of quark, but protons and neutrons consist of just two types - "up-quarks" and "down-quarks".
    • • How many up-quarks and down-quarks are protons and neutrons made of? [2]
        • A proton is made of 2 up-quarks & 1 down-quark
        • A neutron is made of 1 up-quark & 2 down-quarks

  • If protons and neutrons are made of the same thing, why is one (the proton) electrically positive and the other (the neutron) electrically neutral? [2]

    • Each quark has a charge (just like electrons).
    • Up-quarks have an electrically positive charge (2/3 the strength of a positron's positive charge)
    • Down-quarks have an electrically negative charge (1/3 the strength of an electron's negative charge)

  • If a proton and neutron are made of the same thing, can you change a proton into a neutron (and vice-versa)? [2]

    • Yes - Sometimes the number of protons and neutrons in a nucleus can make the nucleus unstable. To become more stable, a neutron is converted into a proton (or vice-versa)
      • How does this happen? [1]
        • This happens by changing a down-quark into an up-quark (or vice-versa).
          • Won't this change the overall charge of the particle? [1]
            • In order to keep the overall charge the same, an electron (or positron) is also created to balance it out.

• Classwork

  • 1) Name two fundamental particles
  • 2) What does it mean to say a particle is fundamental?
  • 3) What particles are neutrons made from?
  • 4) Add together two up-quarks and a down-quark. What do you get?
  • 5) Describe what happens to the quarks in a neutron during beta-decay.
  • 6) Why must an electron be produced when a neutron turns into a proton?
  • 7) Make simple sketch diagrams of a proton and a neutron, showing the number and type of quarks
  • 8) Complete the following sentence: "In beta decay, a proton is converted to a ............................ and a ................................ is emitted".
  • 9) Describe beta-decay interms of what happens to the quarks in a proton
  • 10) Scientists at CERN carry out experiments involving smashing particles together at high speeds.  Fill in the gaps in the pasage:  "In an experiment, two protons are .......................... to very high speeds and made to collide. This collision releases a large amount of ...................... Some of this ...................... can be turned into mass which is equal parts ........................ and anti............................

• Homework

  • 1) Many particles can be split into even smaller particles.
    • What is a fundamental particle?
  • 2) Say whether each of the following is a fundamental particle or not:
    • Proton
    • Electron
    • Neutron
    • Monkey
    • Positron
    • Alpha particle
  • 3) Choose the statements that are true
    • Quarks are made up of protons and neutrons
    • The relative mass of a quark is 1/3
    • All quarks have the same charge
    • There are 2 quarks in a proton
    • There are 2 types of quark in a neutron
  • 4) Match the particles on the left with the correct description of their properties
    • Electron.............................relative mass 1/3, relative charge 2/3
    • Down-quark.......................relative mass 1, charge +1
    • Proton...............................fundamental particle, charge -1
    • Neutron.............................relative charge -1/3
    • Positron.............................made up of two down-quarks and one up-quark
    • Up-quark...........................fundamental particle, charge +1
  • 5) The number of protons and neutrons in a nucleus can make it unstable. Complete the following passage by choosing from the words in brackets ( proton / beta decay / neutron / electron )
    • To become more stable, the nucleus can convert a neutron into a(n) ..............................
    • To keep the overall charge zero, the nucleus must emit a(n) ................................
    • This process is called ...............................
  • 6) Antimatter is made up of antiparticles
    • Give on similarity between a particle and its antiparticle
    • Give on difference between a particle and its antiparticle
    • Name the antiparticle of the electron