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Radioactivity により Mind Map: Radioactivity

1. Alpha particle scattering experiment--Rutherford

1.1. 1. most alpha particles go through foil in straight line.

1.1.1. most of the atom is empty space

1.2. 2. some alpha particles were deviated with angles less then 90 degree.

1.2.1. nucleus takes positive charge

1.3. 3. only a few alpha particles were deviated with large angles greater than 90 degess.

1.3.1. mass and charge of atom concentrated in a small volume

2. Simple model of nuclear atom

2.1. proton and neutron in the nucleus and electron around the nucleus

3. Isotopes

3.1. Atoms of the same element that have same proton number but different number of neutron.

4. Representation of nuclides

4.1. Nuclides: special combinations of protons and neutrons

5. Conservation

5.1. nucleon number

5.2. proton number

5.3. mass-energy

6. Radiation

6.1. Total number of nucleons remains constant as does the total number of mass of the nucleus is converted to energy of the emitted radiation--mass-energy conservation

6.1.1. Alpha

6.1.1.1. Helium nucleus contains 2 protons and 2 neutrons

6.1.1.2. strong ionising power, but short range, only can travel few cm in the air

6.1.1.3. positively charged

6.1.1.4. daughter particle has less mass than original particle before emitting radiation --> mass lost has been converted into energy as the source of kinetic energy of alpha particle. the total mass-energy is conserved.

6.1.1.5. a few cm in the air, stopped by a few sheets of paper

6.1.1.6. equations

6.1.2. Beta

6.1.2.1. Beta-

6.1.2.1.1. neutron in the nucleus changes into a proton and a high energy electron which is emitted

6.1.2.1.2. mass number stays the same, proton number increases by 1

6.1.2.1.3. A very light, electrically-neutral antiparticle called antineutrino is also emitted. conservation of electric charge required this particle to be electrically neutral

6.1.2.1.4. equations

6.1.2.2. Beta+

6.1.2.2.1. when a proton decays into a neutron and a high energy positron and electron neutrino.

6.1.2.2.2. mass number stays the same, proton number decrease by 1

6.1.2.2.3. equations

6.1.2.3. around 1 m in the air, stopped by several mm of aluminium

6.1.3. Gamma

6.1.3.1. high energy electromagnetic radiation

6.1.3.2. nucleus changes shape into a more stable shape, gamma radiation (gamma ray) emitted as a result

6.1.3.3. gamma decay can occur alongside alpha and beta decay, when an unstable nucleus adjusts to a more stable energy level.

6.1.3.3.1. mass-energy is conserved in nuclear reaction, energy might be released by gamma rays when sum of the masses on the left-hand side of the equation is not the same as right-hand side.

6.1.3.4. not affected by electric and magnetic fields

6.1.3.5. unlimited range in air, stopped by several cm of lead

6.1.3.6. equations

7. Fundamental particles

7.1. not consist of combinations of other particles

7.2. e.g. lepton (electron)

8. Weak interaction between quarks

8.1. The role of it in the transmutation of quarks makes it the interaction involved in many decays of nuclear particles which require a change of quark from one flavor to another. Neutrino interaction induces beta decay.

9. Distinguish between nucleon number and proton number

9.1. proton number=nucleon number -neutron number=electron number

9.2. nucleon number = atomic mass number

10. Matter and antimatter

10.1. If a particle collides with its antiparticles, they annihilate each other, producing photons.

11. Deflection in electric field

11.1. alpha and beta particles are deflected in opposite directions in the uniform electric field, but gamma rays are undeflected as they have no charge

11.2. the force on an alpha particle is twice as large as the force on an electron moving at the same speed.

11.3. but the deflection of the alpha particle is much smaller due to its much larger mass

12. Subatomic particles

12.1. Hadron

12.1.1. composed of quarks, particles affected by strong nucleus force, subject to strong and weak force, bulky

12.1.1.1. meson: 2 quarks -> quark and antiquark

12.1.1.2. baryon: 3 quarks

12.1.1.2.1. proton: baryon number: +1

12.1.1.2.2. neutron: baryon number: +1

12.2. Leptons

12.2.1. particles that are unaffected by strong nuclear force, subject to weak force, light

12.2.1.1. neutrinos

12.2.1.2. electron

12.2.1.3. muon

12.2.1.4. tau

12.2.2. charge: -1

12.2.3. fundamental particle

13. quark

13.1. + 2/3 e

13.1.1. up, u

13.1.2. charm, c

13.1.3. top, t

13.2. - 1/3 e

13.2.1. down, d

13.2.2. strange, s

13.2.3. bottom, b

14. For reaction to occur

14.1. they must have same charge, baryon number (B) and electron lepton number (Le)