1. Half Lifes

2. Atoms Proton Electron Cloud Neutron

3. Atomic Number Number of protons – change this → change the element Hydrogen has one proton and one electron Atomic number = 1 Uranium has 92 of each Atomic number …

4. Atomic Mass Number Neutrons are neutral but do add mass to the nucleus The atomic mass number indicates the total number of protons and neutrons in the nucleus Carbon 14 (6 protons and 8 neutrons)

5. Radioactive Decay Unstable Nuclei sometimes decay Uranium-238 – alpha decay ejects a helium nucleus leaving Thorium -234 – Atomic number is changed – new element

6. Radioactive Decay Carbon-14 (6 protons, 8 neutrons) decays by emitting an electron when neutron → proton – Daughter isotope has 7 protons and 7 Neutrons – Nitrogen-14 – Beta Decay

7. Half life Atoms can decay in a predictable way The time it would take for half of the atoms of a sample to decay

8. Half life example Suppose we find a rock with a mass of 100 grams that is entirely carbon-14 Carbon 14 decays to Nitrogen 14 with a half life of 5730 years This means that after this amount of time our rock will contain 50 grams of carbon 14 and 50 grams of Nitrogen 14 After an additional 5730 years we’ll have 25 grams of carbon 14 and 75 grams of Nitrogen 14