1. Isotopes & Radioactive Decay

2. Electromagnetic Spectrum
Radiation
High energy rays and particles emitted by radioactive sources. (most invisible to human eyes)
Includes: electromagnetic spectrum, alpha & beta particles.
Electromagnetic Spectrum
Radioactivity – release of high energy particles and rays of energy from substance as a result of changes in the nuclei of its atom
Use radioactivity for medical diagnoses by generating electricity
Light is form of radiation visible to us
Radio waves – TV, cell phones, radio, etc, Infrared – warm objects – human body, ovens, curling iron, stovetop, remote controls, UV – the sun & black lamp, XRAY –cat scan (dentists and hospitals, airports), gamma rays – cancer treatments

3. Radioactivity
The release of high-energy particles and rays from a substance due to changes in the nuclei of its atoms.
Naturally occurring radiation found in our environment is called:
“Natural Background Radiation”
Natural background radiation – stream of high energy & fast moving particles found in environment
Roentgen discovered energy emitted from materials when he bombarded them w/ electrons  unknown rays “X” rays
French physicist Becquerel – discovered that uranium salts emitted rays that darkened photographic plates – caused photographs to be exposed
Radioactive material (Iron-59) releases energy which is detected by equipment to make images of body parts
Radioactivity can be useful, such as in medical diagnoses and treatment (X-rays, Chemotherapy, etc.) and in generating electricity (Nuclear power plants)

4. Isotopes Atoms of the same element that have the…
Same number of protons (same atomic number)
Different number of neutrons
Since the number of neutrons differs, the mass number also differs.
Mass number = protons + neutrons
Different isotopes of the same element all have:
The same chemical symbol
The same atomic number (# of protons)
Different mass numbers

5. Representing Isotopes
Use standard atomic notation
Symbol + Atomic number + Mass number
Also called “Nuclear Symbol” X
Mass #
Atomic #
e.g.:
Potassium has 3 naturally occurring isotopes. 39 K 40 K 41 K 19 19 19
K = on periodic table potassium has mass of 39.1 – we will see why
Mass # = superscript
Atomic # = subscript
Potassium-39
Potassium-40
Potassium-41
Protons 19 19 19
Neutrons 20 21 22
Electrons 19 19 19

6. Atomic Mass
In nature, most elements are found as a mixture of isotopes.
Potassium-39
Potassium-40
Potassium-41
93.26%
0.01%
6.73%
Each banana has the same relative abundance of potassium isotopes
The atomic mass of an element is the average of all the naturally occurring isotopes.
Potassium has 25 known isotopes from K32 to K56
Those are the 3 naturally occurring isotopes
39 and 41 are stable
Atomic mass = (.9326 x 39) + (.0001 x 40) + (.0673 x 41) = 39.1

7. Assignment Classwork: Homework: Practice Problems Q. 1-4 Page 291
“Isotopes” Worksheet
Homework:
“Isotopes and Ions” Worksheet