1. Anatomy of an Atom Parts of an Atom Nucleus (positive, mass of 1 amu) Neutron (, mass of 1 amu) Electron Cloud Electrons (, negligible mass)

2. The Periodic Table Atomic = # of (determine the type of atom); also # of for neutral atoms Atomic mass = # of protons + # of

3. Different Versions of an Atom are atoms that have a positive or negative charge; p ≠ e are atoms of the same element that differ in their number of (same atomic #, different atomic mass)

4. What is Radioactivity? Spontaneous decay () of the nucleus of an atom, usually releases (emits) a particle &/or energy Can’t when an atom will decay Can’t change the of decay (heat, electric, etc.)

5. Nuclear Radiation Some nuclei are. Unstable nuclei decay and release a particle (alpha or beta) or energy (gamma) Nuclei can change into different when they decay. Types of : alpha particles, beta-particles, gamma rays What makes things radioactive? What happens during radioactive decay?

6. Alpha Particles (a) Alpha particles are made of 2 and 2. Helium results (+) charged Massive Barely pass through a. Remove electrons from matter as it passes through. () What type of particles are emitted during radioactive decay?

7. Beta particles are formed from break down of a neutron into 1 e- and 1 proton. (-) charged Fast-moving The e- is thrown from nucleus. Faster than particles Stopped by a of metal Ionize other atoms A element forms Beta Particles (ß)

8. Gamma rays (γ) Electromagnetic energy stronger with frequency and lower than light or X- rays No but they do ionize cause damage because of high energy that. Concrete or 1.5 cm of lead can stop it from traveling through

9. What do they all have in common? Ionizing- creates particles (ions) Detectable (with counter) Harmful to tissue From the of atoms

10. Half Life Time it takes for of the substance to. Different half-lives for different Can be used to predict how old something is. The half life of sodium-25 is 1 minute. How much of a 100 g sample of Na-25 would be left after 1 minute? How much would be left after 2 minutes?

11. Nuclear Forces Stability of an atom depends on the force that the nucleus together (force). Acts between protons and neutrons. Neutrons act as “nuclear ” to prevent protons from flying apart Only happens over a short distance. Can’t hold beyond p+ Nuclei with too many or too few are unstable and become radioactive. More than protons- always unstable, decay More Nuclear Decay

12. Fission vs Fusion Fission is the down of a nucleus Fission can start chain reactions Fusion is nuclei Both release energy (E = mc 2 ) E= energy m= mass c = speed of light (3 X 10 8 )

13. Helpful radiation Can be natural-soil, sun, water, plants Our sun emits solar radiation Can actually change DNA and cause birth defects Smoke alarms Treat cancer Tracers in medicine Tracers in geology Nuclear power- fission Radiation in our world