Fichas
Radioactivity
Fichas del conjunto (10)
- 1Plum Pudding Theory (JJ Thomson)Atoms are spheres of positive charge with tiny negative electrons stuck in them like plums in a plum pudding.
- 21909 Rutherford and Marsden experimentThey tries firing a beam of alpha particles at thin gold foil. Most the alpha particles went straight through, but the odd one came straight back.
- 3What the Rutherford and Marsden experiment proved (3)1. Most of the mass of the atom was concentrated at the centre in tiny nucleus.
2. The nucleus must have a positive charge, because it repelled the positive alpha particles.
3. Most of an atom is just empty space. - 4Isotopes and Radioactivity1. Most elements have different isotopes, but there's usually only 1 or 2 stable ones.
2. The rest tend to be radioactive, meaning they decay into other elements and also give out radiation. - 5Radioactivity ProcessIt is completely random. It is also completely unaffected by physical conditions such as temperature. Radioactive substances spit out at least one of alpha, beta or gamma radiation.
- 6Where Background Radiation comes from (3)1. Naturally occurring unstable isotopes - in the air (51%), food (12%), building materials and rocks(14%).
2. From space (mostly the sun), known as cosmic rays (10%).
3. From man-made sources, i.e. the nuclear industry (although only contributes 1%). - 7Radiation - Alpha Particles (4)1. An alpha particle is 2 neutrons and 2 protons (a helium nucleus).
2. They are big, heavy and slow moving.
3. Therefore they don't penetrate far into materials, stopped quickly, even in air.
4. They are strongly ionising, meaning they bash into a lot of atoms and knock electrons off them, creating ions. - 8Radiation - Beta Particles1. They are electrons.
2. They're small and move quite fast.
3. - 9Radiation - Gamma Rays1. They are electromagnetic waves with a very short wavelength.
2. They penetrate far without being stopped and pass straight through air.
3. They are weakly ionising because they usually pass through rather than collide with atoms.
4. They have no mass and no charge. - 10—