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Radioactivity により Mind Map: Radioactivity

1. Atom

1.1. a positively charged nucleus - made of protons - and neutrons surrounded by negatively charged electrons

2. Isotopes

2.1. isotopes are atoms of the same element, but with different masses

2.2. they have the same number of protons but different number of neutrons. e.g. Carbon-12, Carbon-13 and Carbon-14

3. Radiation Decay

3.1. decay occurs in random and spontaneus process

3.1.1. Alpha (a helium nucleus) - highly ionising - weakly penetrating

3.1.2. Beta Minus (electron) - medium ionising - medium penetration

3.1.2.1. Neutron becomes proton, and an electron is released

3.1.3. Beta Plus (positron) - medium ionising - medium penetrating

3.1.3.1. Proton becomes neutron, and releases a positron

3.1.4. Gamma (radiation) - low ionising - highly penetrating

4. Background Radiation

4.1. weak radiation that can be detected from natural/ external sources

4.1.1. Cosimic Rays

4.1.2. Radiation from underground rocks

4.1.3. Nuclear fallout

4.1.4. Medical rays

4.1.5. Radon gas from the ground

5. Methods of Measuring Radioactivity

5.1. Photographic film

5.2. Geiger-Muller Tube

6. Atomic Structure

6.1. JJ Thomason discovered the electron 1897 The Plum Pudding Model was formed

6.2. Rutherford realised most of the atom was empty space 1911 The Gold Foil Experiment

6.3. Bohr produced the final model of the atom 1913

6.4. Rutherford Model 1913

7. Half-Life

7.1. It cannot be predicted when any one nucleus will decay, but the half-life is a constant that eneables the activity of a very large number of nuclei to be predicted.

7.2. the half-life of an isotope is the time taken for half the nuclei in a sample to decay. Or the time taken for the activity of a sample to decay by half.

8. Uses of Radioactivity

8.1. Smoke alarms (alpha)

8.2. Irritating food (gamma)

8.3. Sterilisation of equipment

8.4. Tracing and gauging thickness

8.5. Diagnosis and treatment of cancer

9. Dangers of ionising radiation

9.1. short half-life: initially very radioactive but quickly dies down (less long term risk)

9.2. long half-life: remains weakly radioactive form a long period of time

10. Safety Measures

10.1. limiting patient dose use radioactives with short half-life

10.2. limiting risks to medical personnel leave room during radioactive tests (everyday proximity puts them at risk)

11. Nuclear Power

11.1. waste disposal is difficult

11.2. radiation leaking- safety risk. Chain reaction becomes uncontrollable and causes a meltdowm

11.3. no CO2 is produced

12. Nuclear Energy

12.1. Fusion: The process of small nuclei being forced together (under immense temperature and pressure) to form a heavier nucleus

12.1.1. Energy source for stars

12.1.2. Electrostatic repulsion of the protons = a lot of energy is required to bring the nuclei close enough to fuse

12.1.3. Cannot happen at low temperatures or pressures

12.1.4. Difficult to make a practical and economic fusion power station

12.2. Fission: The process of a nucleus splitting into two smaller nuclei after absorbing neutrons which releases more neutrons.

12.2.1. Uranium-235 is the fuel used in nuclear (fission) power stations

12.2.1.1. it absorbs neutrons and becomes unstable = fission.

12.2.1.1.1. releases energy

12.2.1.1.2. forms two 'daughter' nuclei

13. Chain reaction

13.1. after one neutron splits, emitting neutrons, these neutrons cause further fissions, which releases more neutrons..chain reaction. = must be controlled

13.2. As the more neutrons are released than the number absorbed, this could cause an exponential process.

13.2.1. Moderators: water/graphite = slows down the emitted neutrons to be absorbed for further fissions (fast moving neutrons cannot be easily absorbed)

13.2.2. Control rods: boron rods in the reactor core which absorb excess neutrons, preventing a runaway chain reaction.

13.3. heat energy from the chain reaction is absorbed by water (coolant) which evaporated into steam, and is used to turn a turbine, which turns the generator which generated electricity.