1. 1.4 Isotopes, Radioisotopes and Atomic Mass

2. Recall Standard Notation for an Element

3. Isotopes
Frederick Soddy was the first to propose the theory of isotopes
Different isotopes of a given element have the same atomic number but different mass numbers since they have different numbers of neutrons
Chemical properties of the different isotopes of an element are identical, but they will often have great differences in nuclear stability
Some elements consist of one isotope but many consist of a mixture of isotopes

4. as a result of isotopes, unified atomic mass units (amu) are used to calculate the mass number of elements
only 80 elements have any stable isotopes
Isotopic Abundance is the percentage of an isotope in a sample
A Mass Spectrometer is a tool used to distinguish isotopes and their abundance in a sample

5. Mass Spectrometer

6. Radioisotopes
some elements have isotopes that are unstable and as they decay they emit radiation
it can be a quick or slow process depending on the isotope
the radiation they emit can be harmless or lethal
there are 3 main types of nuclear radiation: alpha particles, beta particles and gamma rays

8. Radioactive decay and Half-life
The concept of radioactive decay was discovered by a Canadian scientist- Harriet Brooks ( )
Half-life is the amount of time required for ½ of the nuclei in a radio active sample to decay
Half lives of radioisotopes vary considerably from element to element

9. Ex: a by product of forming uranium for nuclear reactors is radium-226 which has a half-life of years or annum (a). If your sample is initially 25g, how much would remain after:
a) one half-life
b)five half-lives

10. Uses of Radioisotopes Smoke detectors- Americium-241
Agricultural Applications- phosphorus-32
Food Irradiation - cobalt-60
Archaeological Dating carbon -14
Medical- various tracers that are given and help image various tissues or bone in a scan

12. Finding the Mass given Isotopic Abundance
Silicon has three isotopes Si-28, Si-29, and Si 30. In a sample 92.8% of the atoms are Si-28 with a mass of , 4.70% of the atoms are Si-29 with a mass of and 3.02% of the atoms are Si-30 with a mass of Calculate the average atomic mass of silicon.