1. Radioactivity & Half-life Atoms: Made of 3 parts Protons have mass and are found in the nucleus-Positive charge Neutrons have mass and are found in the nucleus-Neutral no charge Electrons very little mass found in the energy levels around the nucleus

2. Radioactivity & Half-life Hydrogen is the smallest atom and is the most common found in the universe. It’s atomic mass is 1 because it has 1 proton. Helium is the 2 nd atom with an atomic mass of 4 because has 2 protons + 2 Neutrons

3. Carbon: is the atom that composes all life forms on earth! Carbon has 6 protons and 6 neutrons so it has an atomic mass of 12. Known as C12. Most Carbon is C12 but some are C13 or C14 C13 and C14 are radioactive forms because they have extra neutrons. C12 becomes radioactive when the energy from the sun causes the neutron into a C12 atom.

4. Radioactivity & Half-life We consume some C14 when we eat plants or animals. This C14 becomes part of our bones. When a tree or animal dies it no longer takes in more C14. Over time the C14 decays (loses energy) to become N14.

5. Radioactivity & Half-life http://science.howstuffworks.com/environmental/earth/geology/carbon- 14.htm Radio carbon dating determines the age of ancient objects by means of measuring the amount of carbon-14 there is left in an object. A man called Willard F Libby pioneered it at the University of Chicago in the 50's. In 1960, he won the Nobel Prize for Chemistry. This is now the most widely used method of age estimation in the field of archaeology. Half-life is the time required for a quantity to fall to half its value as measured at the beginning of the time period. Because the half-life of carbon-14 is 5,700 years, it is only reliable for dating objects up to about 60,000 years old.

6. http://phet.colorado.edu/en/simulation/radioactive-dating-game So if an organism has 100 C14 atoms when it dies, it will take about 5700 years for 50 of those to decay into Nitrogen 14. It will take 5700 years more for 25 of the 50 remaining to decay to N14. It will take 5700 years more for half of the 25 remaining to decay to N14. This continues until there is no more C14. Explore this site below to understand how half-life helps scientists determine the age of fossils and rocks.

7. Using radioactivity and half-life we can determine the age of earth, rocks and the many forms of life on earth.