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| Questão | Responda |
| what is the total number of protons and neutrons? | mass number |
| what is the effect of magnetic and electric fields on alpha, beta and gamma rays | alpha and beta are deflected gamma is not |
| what is the total number of protons called? | atomic number |
| some subastances give out radiation from where? | the nuclei of their atoms, these are radioactive substances |
| where does background radiation come from? | - unstable isotopes everywhere.. food, air, rocks -space (cosmic rays from the sun) -man made sources.. fallout from nuclear weapons or dumped nuclear waste |
| what is an alpha particle? | two neutrons and 2 protons (same as helium) |
| what is a beta particle? | an electron from the nucleus |
| what is gamma radiation? | electromagnetic radiation |
| 1 use of alpha radiation | smoke detectors- smoke from a fire absorbs alpha radiation, altering the ionisation and triggering the alarm. |
| use of beta radiation | Radiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium. The thicker the material, the more radiation is absorbed and the less radiation reaches the detector. |
| Use of gamma radiation | Gamma radiation is used in the treatment of cancer, testing equipment and sterilising medical instruments. |
| what are 3 properties of alpha particles? | -strongly ionising -they dont penetrate far into materials - stopped quickly even in air |
| what dangers are there with an alpha particle | -fairly unharmful outside the body because they do not penetrate the skin -if swallowed very dangerous because they are so strongly ionising they can change the dna of cells making them cancerous and causing them to multiply out of control |
| what are 3 properties of beta particles? | moderately ionising -long range in air -moderate penetration into materials. |
| what are the dangers accosiated with beta radiation. | particles have a longer range than alphas, but ionise much less strongly. Therefore they dont do as much damage as alpha. However, they do have more penetrating power, which means that they can get through your skin and affect cells inside you. |
| Dangers associated with Gamma radiation. | gamma rays are very difficult to stop, When they are absorbed by an atom, that atom gains quite a bit of energy, and may then emit other particles. If that atom is in one of your cells, this is not good! |
| what is the half life of an isotope? | the average time it takes for the number of nuclei of the isotope sample to halve, or the time it takes for the count rate of a sample containing the isotope to fall to half its original level |
| name 3 properties of gamma radiation | -weakly ionising -penetrate far into materials -pass straight through air |
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Image:
half_life (image/jpg)
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2 hours |
| what is the basic structure of an atom? | a small central nucleus composed of protons and neutrons surrounded by electrons |
| what is the basic structure of an atom? | a small central nucleus composed of protons and neutrons surrounded by electrons |
| what is the relative atomic mass of a proton and a neutron? | 1 |
| what is the relative atomic mass on an electron? | 0 |
| name the 2 features of the plum pudding model | the positively charges matter were evenly spread in the 'pudding' -- the negative electrons were burried inside the modle |
| who disproved the plum pudding model? when? | rutherford and marsden 1909 |
| how was the plum pudding model disproved? | they tried firing a beam of alpha particles at thin gold foil. They then measured the number of alpha particles per second through different angles |
| what charge does and atom have? | no charge |
| atoms may lose or gain electrons to form what? | ions |
| what were the results of the experiment? | 1) most alpha particles passed through the foil 2) number of deflected alpha particles decreased as angle of deflection increased 3)1 in 1000 alpha particles deflected by more than 90 degrees |
| whats is the different feature of an isotope? | different number of neutrons |
| what was deduced from these results? | 1) there was a nucleus where most of the mass was concentrated 2) the nucleus was positively charged as it repelled alpha particles 3)the nucleus was much smaller than the atom |
| why was the theory accepted? (3) | it explains radioactivity in terms of what happens to an unstable nucleus 2) it predicted the existence of the neutron, which was later discovered 3) it agreed with all current results from experiments |
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