1. When Atoms Change- Ions

2. What happens if the number of electrons change??? If an atom gains electrons… 1. The charge becomes negative. (There are more negative e- than positive p+ now!) 2. The mass stays the same (electron ’ s mass = 0). 3. The number of protons and neutrons stays the same. If an atom loses electrons… 1.The charge becomes positive. (There are less negative e- than positive p+ now!) 2.The mass stays the same (electron ’ s mass =0). 3. The number of protons and neutrons stays the same.

3. The atom is now called an ION!!! When atoms gain or lose electrons! Ions are charged particles!

4. Charged Ions Anion (-) Negatively charged ion. Cation (+) Positively charged ion

5. ION EXAMPLE H+ is a positive hydrogen ION H: Is the neutral hydrogen atom H- : is a negative hydrogen ION

6. Ion Practice Na Be I Ca Ga S P C

7. How are isotopes and ions similar and different? (setup a T chart) (hint* think about particles, masses and charges) Similarities Same number of protons only! Differences Diff Masses Diff Charges Diff Number of electrons Diff Number of neutrons

8. How are neutral atoms and their isotopes similar and different? (Set up a “ T ” chart) Similar Same element Same # of protons Same # of electrons Same charges Different Different masses Different # of neutrons

9. Reviewing Isotopes What are isotopes gaining or losing? Here is an Atom of Oxygen (how many neutrons?) Atomic Mass=16 These are isotopes of Oxygen O-17O-18 So…How many neutrons does each isotope of Oxygen NOW have? 8 neutrons Neutrons! 10N9N

10. How are neutral atoms and their isotopes similar and different? (Set up a “ T ” chart) Similar Same element Same # of protons Same # of electrons Same charges Different Different masses Different # of neutrons

11. Everyday Uses of Isotopes Smoke Detectors and Americium-241 What most consumers don't know is that many of these units contain a small amount of americium-241. By utilizing the radioactive properties of this material, smoke from a fire can be detected at a very early stage. This early warning capability has saved many lives. In fact, studies have shown that 80% of fire injuries and 80% of fire fatalities occur in homes without smoke detectors.

12. Carbon-14 Dating Recalling that all biologic organisms contain a given concentration of carbon-14, we can use this information to help solve questions about when the organism died. When an organism dies it has a specific ratio by mass of carbon-14 to carbon-12 incorporated in the cells of it's body. At the moment of death, no new carbon-14 containing molecules are metabolized, therefore the ratio is at a maximum. After death, the carbon-14 to carbon-12 ratio begins to decrease because carbon-14 is decaying away at a constant and predictable rate. Remembering that the half-life of carbon-14 is 5700 years, then after 5700 years half as much carbon-14 remains within the organism.

13. Food Irradiation Food irradiated by exposing it to the gamma rays of a radioisotope -- one that is widely used is cobalt-60. The gamma rays pass through the food to destroy many disease-causing bacteria as well as those that cause food to spoil. It ’ s not strong enough to change the quality, flavor or texture of the food. The food never comes in contact with the radioisotope and is never at risk of becoming radioactive!