1. Isotopes, Stability, and Radioactivity How can you tell if an isotope is stable or not?

2. Objectives To predict if an isotope will be radioactive or not based on  the ratio of Neutrons:Protons  Using a Stability Chart To compare and contrast:  Ionizing radiation  Non-ionizing radiation

3. Vocabulary Nuclear Chemistry: the study of the nucleus, and the effect if we change the number of protons and/or neutrons Radioactivity: Happens when unstable isotopes give off atomic sub-particles and energy in order to become more stable.  What are atomic sub-particles given off?  Protons & Neutrons

4. How do we know if an isotope is radioactive? Protons and Neutrons are in the nucleus. Protons are positively charged and should repel each other. The nuclear force is the force that holds the nucleus together. The nuclear force is stabilized by having an appropriate number of neutrons to stop the protons from repelling each other. When the amount of neutrons is too high or low, the nucleus becomes unstable. Radioactive isotopes will give off protons, neutrons, and or energy until the nucleus becomes stable.

5. Look at its’ atomic number and calculate the ratio of neutrons:protons. This is a rough estimate if you are not given a Stability chart. What is stable?  Atomic # 1-20 AND neutrons: protons is 1:1  Atomic # 21-83 AND neutrons:protons is 1.5 : 1 Any isotope outside of this ratio (big or small) is radioactive. All atoms with more than 83 protons (bismuth) are radioactive no matter the ratio. How do we know if an atom is radioactive?

6. Examples: 1. Is Polonium-212 stable? No, it has an atomic number greater than 83 2. Is potassium-42 stable? # neutrons: 42-19 = 23 # protons: 19 #neutrons:protons = 23/19 =1.2 : 1 For an atomic # >20, it should be 1.0 Therefore, no it is not stable. 2. Is calcium 40 stable? # neutrons: 40-20 = 20 # protons: 20 #neutrons:protons = 20/20 = 1.0 : 1 For an atomic # >20, it should be 1.0 Therefore, yes it is stable.

7. Stability Chart Most accurate way to determine if an isotope is stable or not. Look up based on number of protons and neutrons. If the isotope is on the band, it is stable. If it sits on top of the band, it has too many neutrons If it is under the band, it has too many protons Atomic # >83 has too many neutrons & protons Too Many Neutrons Too Many Protons & Neutrons Too Many Protons

8. Examples: 1. Is Carbon-14 stable? # neutrons: 14-6=8 # protons: 6 No. 2. Is Calcium-40 stable? # neutrons: 40-20=20 #protons: 20 Yes 3. Is zinc-60 stable? # neutrons: 60-30=30 # protons: 30 No.

9. Radiation waves Radiation — the energy given off from a source in the form of waves or particles and can travel great a distance.  Think about the ripples of water that radiate outwards in a pond after a pebble is dropped into the water Examples of sources :  Light bulbs  The sun  A radio  A microwave There are many different types of radiation

10. Main Types of Radiation Non-ionizing Radiation – has lower levels of energy The energy is so low, that it is not strong enough to affect the atoms it comes in contact with.  Examples: visible light, radiowaves, microwaves, infrared rays from a heat lamp Ionizing Radiation – has higher levels of energy This high energy radiation will affect the atoms it comes in contact with, including human tissue which it will pass through.  Examples: x-rays, gamma rays

11. Ionizing Radiation: Effects and can cause damage to atoms