1. Subatomic Physics Chapter 25-1

2. Properties of the Nucleus The nucleus is the small, dense core of an atom. Atoms that have the same atomic number but different neutron numbers are called isotopes.

3. Properties of the Nucleus A particle has a certain amount of energy (rest energy) associated with its mass.

4. Nuclear Stability The nucleus of an atom is able to exist because of a nuclear force called a strong force. Strong force is the attractive force between the protons and neutrons.

5. Nuclear Stability Neutrons help to stabilize a nucleus.

6. Binding Energy Energy involved when components of a nucleus are forced together or split (fusion/fission).

7. Nuclear Decay Ch. 25-2

8. Nuclear Decay Nuclear decay can happen in nature or induced artificially. When a nucleus decays radiation is emitted as particles, photons or both.

9. Nuclear Decay Modes An unstable nucleus can decay in three ways:

10. Measuring Nuclear Decay The decay constant indicates the rate of radioactive decay. Half-life measures how long it takes half a sample to decay

11. Decay Example

12. Nuclear Reactions Ch. 25-3

13. Nuclear Reactions A change in the nucleus of an atom is called a nuclear reaction. Fission – a nucleus splits into two or more nuclei. Fusion – one or more nuclei combine.

14. Nuclear Chain Reaction

15. Nuclear Bomb If a chain reaction happens too fast, it could result in a violent explosion. This is the principle behind the first nuclear bomb.

16. Nuclear Reactors A nuclear reactor is a system designed to maintain controlled self sustained chain reactions. All nuclear reactors operate through fission. Fusion occurs naturally only for light atoms.

17. Particle Physics Ch. 25-4

18. Four Fundamental Interactions All particles in nature are subject to four fundamental interactions : Strong – “glue” that holds nucleons together ; strongest Electromagnetic – attraction of unlike and repulsion of like charges. Weak – beta decay Gravitational – holds planets, stars, and galaxies together; weakest

19. Four Fundamental Interactions

20. Classification of Particles Electrons and neutrinos are leptons. Protons and neutrons are baryons.

21. Standard Model