 Matter is any thing that occupies space & has mass  Present in three states: solid, liquid, & gas  It could be divided into elements & compounds  Atoms, are the fundamental units of elements

 The fundamental building blocks of nature; they cannot be subdivided into smaller parts by ordinary chemical methods, but could be broken down into subatomic particles (electron, proton, & neutrons) by special high-energy techniques  The atom consists of two parts: 1. Nucleus (positive charged) 2. Electrons (negative charged)  The identity of an atom is determined by the composition of its nucleus & the arrangement of its orbiting electrons.

 In 1913, Bohr imagines the atom as a miniature solar system

The nucleus, or dense core of the atom, is composed of particles known as protons & neutrons  Protons carry positive charges, whereas neutrons carry no electrical charge.  Atoms differ from one another based on their nuclear composition  Mass Number is the total number of protons & neutrons in the nucleus  Atomic Number is the number of protons in the nucleus

Electrons are tiny negatively charged particles that have very little mass  Electrons travel around the nucleus in orbits, or shells  An atom contains a maximum of seven shells, each located at specific distance from the nucleus & representing different energy levels  The shells are designated with the letters K-Q; the K shell is located closest to the nucleus & has the highest energy level  Each shell has a maximum number of electrons it can hold  The number of shells occupied in a particular atom depends on the number of protons in the nucleus

The amount of energy required to remove an electron from it is shell  The electrostatic attraction between a positively charged nucleus & its negatively charged electrons balances the centrifugal force of the rapidly revolving electrons & maintains them in their orbits. Consequently, the amount of energy required to remove an electron from a given shell must exceed the electrostatic force of between it & the nucleus

 The binding energy is determined by the distance between the nucleus & the orbiting electron & is different for each shell  Atoms with fewer protons have lower binding energy while atoms with more protons have higher binding energy

Is the process of removing an electron from electrically neutral atom to produce an ion pair

 Ion is an atom or subatomic particle with a positive or negative charge

 Ionization deals with electrons only & requires sufficient energy to overcome the electrostatic force  The electrons in the inner shells are so tightly bound to the nucleus that only x-rays, gamma rays, & high-energy particles can remove them  In contrast, the electrons in the outer shells have such low binding energies that they can be easily displaced by photons of lower energy (e.g., ultraviolet or visible light)

Radiation that is capable of producing ions by removing or adding an electron to an atom A. Particulate Radiation B. Electromagnetic Radiation

 It consist of nuclei or subatomic particles moving at high velocity 1. Electrons can be classified as beta particles or cathode rays. 2. Alpha particles are emitted from the nuclei of heavy metals & exist as two protons & neutrons, without electrons. 3. Protons are accelerated particles with a charge of Neutrons are accelerated particles with no electrical charge

 Is the movement of energy through space as a combination of electric & magnetic fields  It is generated when the velocity of an electrically charged particle is altered

 Natural Background Radiation  Man-Made Radiation

 Electromagnetic radiations are arranged according to their energies in what is termed the Electromagnetic Spectrum

 Depending on their energy levels, electromagnetic radiations can be classified as ionizing or non-ionizing  In the electromagnetic spectrum, only high-energy radiations (cosmic rays, gamma rays, & x-rays) are capable of ionization

 Have no electrical charge  Have no mass or weight  Travel at the speed of light  Travel as both a particle & a wave  Propagate an electrical field at right angles to path of travel  Propagate a magnetic field at right angles to the electrical field  Have different measurable energies (frequencies & wavelength)

 Quantum theory characterizes electromagnetic radiation as small bundles of energy called Photons or Quanta  Photons are bundles of energy with no mass or weight, which travels as wave at the speed of light & move through space in a straight line, carrying the energy of electromagnetic radiation  The quantum theory of radiation has been successful in correlating experimental data on the interaction of radiation with atoms, the photoelectric effect, & the production of x-rays

 The wave theory characterizes electromagnetic radiations as waves. Such waves consist of electrical & magnetic fields oriented in planes at right angles to one another that oscillate perpendicular to the direction of motion  The wave concept focuses on the properties of velocity, wavelength, & frequency  Wave theory is more useful for considering radiation in bulk when millions of quanta are being examined, as in experiments dealing with refraction, reflection, diffraction, interference, & polarization

1. Velocity (c) refers to the speed of the wave All electromagnetic radiation in vacuum travels at 3 x 10 8 meters/seconds

2. Wavelength defined as the distance between the crest (peak) of one wave & the crest of the next, & is represented by Greek letter lambda (λ)  Wavelength determines the energy & penetrating power of the radiation; the shorter the distance between the crests, the shorter the wavelength & the higher the energy & ability to penetrate matter  Wavelength is measured in nanometers (1 X meters) for short waves (gamma rays) & in meters for longer waves (radio waves)

3. Frequency (ƒ) of a wave refers to the number of cycles per second

 Frequency & wavelength are inversely related; if the frequency of the wave is high, the wavelength will be short, & if the frequency is low, the wavelength will be long

Electromagnetic wave velocity, frequency, & wavelength are related by: C = ƒ λ C = ƒ λ

The amount of energy an electromagnetic radiation possesses depends on the wavelength & frequency; E= 1.24/ λ