11. Particle physics Flashcards
What were the observations from Rutherford alpha-particle scattering experiment?
- The majority of α-particles went straight through (A)
This suggested the atom is mainly empty space - Some α-particles deflected through small angles of < 10
This suggested there is a positive nucleus at the center (since two positive charges would repel) - Only a small number of α-particles deflected straight back at angles of > 90o (C)
This suggested the nucleus is extremely small and this is where the mass and charge of the atom is concentrated
It was therefore concluded that atoms consist of small dense positively charged nuclei, surrounded by negatively charged electrons
Write down the properties of each particle of atom:
proton- charge= +1 and mass=1
neutron- charge=0 and mass=1
electron- charge=-1 and mass- neglible
Define antimatter.
Antimatter particles are identical to their matter counterpart but with opposite charges.
Mention the antimatter of the matter particles- electron, proton and neutron.
Electron -1 = POSITRON +1
Proton +1 = ANTI-PROTON -1
Neutron 0 = ANTI-NEUTRON 0
About Atomic mass unit (u)–
1u = 1.66 x 10 to the power -27 kg
Define these terms-
mass number
atomic number
nucleon number
nuclide
Isotopes
ion
mass number= proton + neutron
atomic number= proton / electron number
nucleon number= proton + neutron
nuclide= specific combination of protons and neutrons in a nucleus
isotopes= nuclei of the same element with equal number of protons but different number of neutrons
ion=an atom that has lost or gained one or more electrons; so it is electrically charged
About alpha particles-
-are high-energy particles made up of 2 protons and 2 neutrons (the same as a helium nucleus)
-They are usually emitted from nuclei that are too large.
- Alpha particles can be stopped by 1 mm of paper.
About beta particles-
- Beta (β−) particles are high energy electrons emitted from the nucleus
- β− particles are emitted by nuclei that have too many neutrons
- Beta is a moderately ionising type of radiation
This is due to it having a charge of +1e
This means it is able to do some slight damage to cells (less than alpha but more than gamma) - Beta is a moderately penetrating type of radiation
Beta particles have a range of around 20 cm - 3 m in the air, depending on their energy
Beta can be stopped by 2 millimetres of aluminium foil
About gamma particles-
- Gamma (γ) rays are high-energy electromagnetic waves
- They are emitted by nuclei that need to lose some energy
-If these particles hit other atoms, they can knock out electrons, ionising the atom
This can cause chemical changes in materials and can damage or kill living cells - Gamma rays can be stopped by 2 cm of lead
- Gamma rays has a speed of light
Define an electron neutrino and about anti-neutrino
An electron neutrino is a type of subatomic particle with no charge and negligible mass which is also emitted from the nucleus.
The anti-neutrino is the antiparticle of a neutrino
Electron anti-neutrinos are produced during β– decay
Electron neutrinos are produced during β+ decay.
Explain the energies during alpha and its graph of no of particles(y) and kinetic energy(x)-
Check the graph in save my exams
When the number of α particles is plotted against kinetic energy, there are clear spikes that appear on the graph
This demonstrates that α-particles have discrete energies (only certain values).
Explain the energies during beta and its graph of no of particles(y) and kinetic energy(x)-
check the graphs in save my exams
When the number of β particles is plotted against kinetic energy, the graph shows a curve
This demonstrates that beta particles (electrons or positrons) have a continuous range of energies
This is because the energy released in beta decay is shared between the beta particles (electrons or positrons) and neutrinos (or anti-neutrinos).
