physics topic four Flashcards
what did John Dalton do
Discovered atoms
what did JJ Thomson do
Discovered electrons
what did Ernest
Rutherford discover
Atoms made of a positive nucleus with
electrons orbiting it.
what did Neils Bohr do
Showed that electrons are found in shells
what did James Chadwick do
Discovered neutrons
what was discovered in the Alpha particle scattering experiment
-Most alpha particles passed straight through therefore most of an atom is empty space
-Some particles were deflected therefore the nucleus is positive (so repels positively charged alpha particles)
-Very few particles bounced back therefore a nucleus is a concentrated small mass
give features of nuclear model of atom
Mass + Positive charge - Concentrated in the middle (nucleus)
Electrons - Orbit the nucleus
in shells
Space - Mostly empty space
give features of plum pudding model of atom
Mass + Positive charge -Distributed around the atom
Electrons - Embedded in
structure
Space - solid mass
what are isotopes
Isotopes are atoms of the same element with the SAME number of protons and a DIFFERENT number of neutrons
how do isotopes that are unstable become stable
Some atomic Isotopes are unstable and emit radiation so they become more stable this process is called Radioactive Decay.
what are the three types of radiation
- Alpha α
- Beta β
- Gamma γ
give a description of alpha radiation
2 Protons and
2 Neutrons
give description of beta radiation
High energy Electron
give description of gamma radiation
High energy Electromagnetic
radiation
describe Penetration power of alpha radiation
Stopped by paper
or few cm’s of air
describe Penetration power of beta radiation
Stopped by few
mm’s of Aluminium
describe Penetration power of gamma radiation
Stopped by cm’s of
lead or metres of
concrete
describe Ionising effect of alpha radiation
Strongly Ionising
describe Ionising effect of beta radiation
Weakly Ionising
describe Ionising effect of gamma radiation
Very Weakly
Ionising
what are the effects of
magnetic/ electric fields on alpha radiation
Weakly deflected
what are the effects of
magnetic/ electric fields on beta radiation
Strongly deflected
what are the effects of
magnetic/ electric fields on gamma radiation
No deflection
describe the effects of gamma radiation on electrons
Electromagnetic radiation absorbed by the electron causes it to move to a higher energy level (shell)
Electron can emit
electromagnetic radiation causing it to return to its original
energy level (shell)
How does radiation kill you
Alpha, beta and gamma radiation collide with DNA,
ionise them (removes electrons), mutating them, giving you cancer
how does low dose radiation effect cells
normal cells exposed to low dose radiation
ionisation inside cell leads to damage
damaged (mutant) cells divided uncontrollably forming a tumour
how does high does radiation effect cells
higher doses tends to kill cells completely, Which causes radiation sickness if lots of cells are killed at once
what is the half life
The half-life is the time taken for the number of radioactive
nuclei in an isotope to half
describe irradiation vs contamination
- Irradiated objects have been exposed to radiation and are NOT radioactive
- Contaminated objects give off radiation as they have been contaminated with radioactive
particles.
how to stay safe when dealing with radioactive sources
- Use tongs and gloves at all times
- Don’t look directly at the radioactive source
what is background radiation
Background radiation is radiation that is found all
around us at all times.
give examples of background radiation
- (medical) x-rays
- radiotherapy
- nuclear weapons (testing)
describe Nuclear Fusion
- Light nuclei
- Fuse to make heavier nuclei
- Some mass converted to energy
describe Nuclear Fission
- Neutron absorbed by an unstable uranium nucleus
- Nucleus splits into 2 daughter nuclei, 3 neutrons, gamma rays and energy
- Neutrons go on to react with more Uranium nuclei
how are control rods used in a nuclear reactor
- Absorb neutrons
- Slowing down the reaction
- Releases less energy
