Revision topic 17 Flashcards
explain the “key” discovery that Henri Becquerel
Henry discovered an image of a key on a film he developed, he realized that uranium salt was on top of that key, so he concluded that the uranium salt had produced some form of radioactivity that went through the paper but not the key leaving an image of the key then he had Marie Curie research more about it
what are the two types of radiation that Ernest Rutherford discovered
- alpha radiation
2. beta radiation
why are some substances radioactive
because they would have an unstable nucleus that would decay and emit radiation, the action of one nucleus to become unstable is completely random
what is background radiation?
it is ionizing radiation from radioactive substances in the environment, in space, and man-made sources
what did Ernest Rutherford deduce from his experiments?
he deduced that there is a nucleus:
at the center of every atom that is much smaller than the atom because alpha particles passed by
where most of the mass of an atom is located
why was rutherford’s nuclear model quickly expected?
because it agreed with the calculations that Marsden and Geiger did, and it explained radioactivity in terms of changes that happen to an unstable nucleus once it emits radiation, and it predicted the existence of a neutron
an unstable nucleus becomes more stable by?
being emitting alpha, beta, or gamma particles
what does an alpha particle consist of?
2 positive protons and 2 nuetrons
what are beta particles?
it is an electron created and emitted by a nucleus that has many neutrons compared to protons
what are the relative mass and relative charge of a beta?
beta particles have a relative mass of 0 but a relative charge of -1
what is alpha radiation stopped by?
a thin sheet of paper
what is beta radiation stopped by?
aluminum sheet
what is gamma radiation stopped by?
thick lead sheet or concrete
what is ionization
is the process of radioactive substances knocking electrons down out of an atom and the atom becomes charged
what is an irradiated substance
a material thats have been exposed to ionizing radiation
the activity of a radioactive isotope is?
the number of atoms that decay per second
what is a count rate of a sample
the number of counts per second
what is the half-life of a radioactive isotope?
it is the average time it takes for the number of nuclei of an isotope in a sample to halve
explain how carbon dating is used to determine the age of an ancient wood
living wood contains a tiny portion of radioactive carbon, when the trees die the number of radioactive carbon decreases, so to find the age of the tree we compare the count rate of the sample with a living wood about the same mass
explain how uranium dating is used to determine the age of igneous rock
the rock contains radioactive uranium that decays into the lead so the scientist would measure the number of lead atoms and uranium atoms
what is nucluer fission
it is the splitting of the atomic nucleus into two smaller nuclei releasing 2 or 3 neutrons and energy
how does nuclear fission occur
it occurs when uranium-235 or plutomium-239 absorbs a neutron and the nucleus splits
whats a chain reaction
it’s an event that occurs in a nuclear reactor and happens when each fission event causes further fission events
whats does the reactor core contain
fuel rods, control roads, and water and high pressure
what is the job of the water in a nuclear reactor
it acts as a moderator that slows down the fission neutrons, it also acts as a coolant to transfer the kinetic energy generated to the heat
what is the job of the control rod in a nuclear reactor
they absorb the neutrons to control the chain reactions
what is nuclear fusion
when two small nuclei release energy when they fuse together to form larger nuclei,
how does fusion happen in the sun
two protons fuse forming heavy hydrogen, then another two protons would do the same thing, after that the two heavy hydrogens would fuse forming helium nuclei and with each fusion energy is realized
whats is the most ionizing radiation
alpha followed by beta then gamma
