Radiation Physics

Chapter 3: The Structure of Matter

Atom

Uncuttable; can not cut

Electron

Very small

Negative charge

Orbits the nucleus in energy levels (or shell)

Proton

2000 times more massive than electron

Resides in the nucleus

Positive charge equal but not opposite to electron charge

Neutron

Mass similar to the proton

Resides in nucleus

No charge (neutral)

Atom

Smallest part of an element

Element

Substance made of one kind of atom

Molecule

Smallest part of a compound

Compound

Substance made of one or more molecules

Transitional Elements

Elements where electrons are added to an inside shell instead of the outermost shell

\-example: elements 21-30

Ionization Potential

Energy need to remove an electron from an atom (thus creating an ion)

Electron Volt

A unit of energy abbreviated eV (it is not a measure of voltage)

Z

Atomic number (number of protons)

A

Atomic Mass (number of nucleons)

Elements

H, He, Li, Be, B, C, N, O….

Isotopes

Atoms of the same element that have different number of neutrons (same atomic number, different atomic mass number, same number of protons)

Isobars

Atoms of different elements that have the same number of nucleons (different atomic number, same atomic mass number)

Isotones

Atoms of different elements that have the same number of neutrons (different atomic number, different atomic mass)

Isomers

Atoms of the same element with the same atomic mass number but with different amount of nucleus excitation (nuclear decay will release different amounts of gamma radiation)

Electron Shell Binding Energy

Energy with which an atom holds onto its electrons

\-different for each shell and different for the same shell of different atoms

\-measure in eV, keV, an MeV

\--1 eV = 1 electron volt

K-shell binding energy is the strongest

Coulomb force between electrons and protons is greatest because the distance between them is least

Positive Ion

Atom missing an electron(s)

Negative Ion

Atom has extra electron(s)

\-an electron by itself is also a negative Ion

Covalent Bonds

Valence elections are shared

Ionic Bonds

One atom gives up its valence electron to another atom

\-NaCl (sodium chloride)

Non-Ionizing Radiation

Certain electromagnetic radiation

\-radio waves, light (below ultraviolet), MRI

No danger to tissue, cells, DNA

Ionizing Radiation

Naturally occurring and manmade kinds

\-ultraviolet (sunlight, tanning beds), Microwave, x-ray, alpha, beta, gamma radiation

Can damage tissue and cell genetic

Radioactivity

Radiation originating from the nucleus of an atom

What are the three types of Radioactivity

Alpha

Beta

Gamma rays

Alpha

\-A particle, Helium nucleus expelled from the nucleus of the atom

\-Doubly Ionized

\-Blocked by skin but, highly carcinogenic if inhaled/ingested

\-**New element is formed** because loss of 2 protons (the forming of a new element through radioactive decay is call **transmutation**)

Beta

\-Positive or negative

\-A particle, electron (e-) or positron (e+ an antielectron) is expelled __from the nucleus__ of the atom

\-Ionization occurs

\-More penetrating than alpha…blocked by thin metal shielding

-Can result in tissue damage

\-New element is formed because of the gain or loss of a proton. Transmutation occurs

Gamma

\-Results from nucleus dropping out of an excited state

\-Not a particle but a high energy electromagnetic wave

\-Ionization occurs. Transmutation __*does not*__ occur

\-More penetrating than alpha or beta…blocked by lead shielding and/or concrete

\-Can result in tissue damage

Radioactive Half Life

Time for one half of the amount of an element to become another element through radioactive decay

Time for a substance to emit only 1/2 of the radioactivity that it did originally