1. Ionization, Radiation and Radioactivity Reference Reading: Chapter 2, pp. 11-13

2.  Now that we have a basic understanding of atomic structure, we can begin to look at a concept called ionization.  Atoms can exist in 2 states: ◦ Neutral (balanced state: positive charge =negative charge) ◦ Electrically unbalanced state

3.  An atom that gains or loses an electron is unbalanced, and is known as an ion.  Ionization is the production of ions.

4.  Ionization produces ions.  An ion pair is produced when an electron is removed from an atom. The result is: ◦ Ejected electron becomes the negative ion ◦ The atom becomes the positive ion ◦ WHY??

6. RadiationRadioactivity  Defined as the emission and propagation of energy through space in the form of waves or particles.  In dentistry, x- radiation is used to produce x-rays.  This is the process by which certain unstable atoms or elements undergo spontaneous disintegration, or decay, in order to attain a more balanced state.  Dentistry does not use radioactive substances to produce dental x-rays.

8.  Can be classified into 2 categories or groups. ◦ Particulate Radiations are  Tiny particles of mass that travel in straight lines and at very high speeds. ◦ Electromagnetic Radiation  Has no mass  Travels at the speed of light 186,000 miles per second  Travels in waves

9.  Electrons are a type of particulate radiation that are classed as either beta particles or cathode rays.  In dentistry, we use the cathode rays in the production of x-rays.  Cathode rays are streams of high speed electrons that originate in the x-ray tube.

10.  These types of radiation are either man made (as in the case of x-rays), or exist in a natural state.

12.  EMR are believed to move through space as both a particle AND as a wave.  The Particle Concept describes them as “discrete bundles of energy” called photons or quanta.  The Wave Concept characterizes their movement by velocity, wavelength and frequency.

13.  Refers to the SPEED of the wave.  All EMR travels at the speed of light – 186,000 miles PER SECOND!!!

14.  The distance between the crest of one wavelength and the crest of the next.  Wavelength determines the energy or penetrating power of the wavelength.

15.  The SHORTER the wavelength, the more penetrating.  The LONGER the wavelength the less penetrating.  Wavelength is measured in nanometers.

16.  Refers to the number of wavelengths that pass through a given point in a certain amount of time.  Frequency high? Wavelength short  Frequency low? Wavelength long