1. Chapter 8 – Section 4 Radioactive Elements

2. Nuclear Reactions Some elements can change into other elements, like uranium thorium, or carbon nitrogen This type of change is Not due to chemical reaction, but due to nuclear reaction (reactions that involve particles in the nucleus).

3. Isotopes All atoms of the same element have the same number of protons. But the number of neutrons may vary in the same element. When this happens, the atoms of that element are called isotopes. Ex: Carbon-12 Carbon- 13 Carbon-14

4. Radioactive Decay Some isotopes are unstable and they undergo nuclear reaction. Their nuclei release fast-moving particles and energy in a process called radioactive decay. There are three types of radioactive decay: alpha decay, beta decay, & gamma decay (types of nuclear radiation).

5. Vocabulary for Ch8 Sec4 composites nuclear reactions isotopes radioactive decay alpha decay beta minus decay beta plus decay gamma decay half-life radioactive dating

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7. Alpha Decay Alpha particle is made of 2 protons + 2 neutrons (equal to a He atom) and it is released by the nucleus of the decaying element. So, the atomic # of the isotope goes down by 2 and the atomic mass goes down by 4. Alpha particle can cause bad burns on the skin, but a sheet of paper is enough to protect you.

9. Beta Decay Two kinds: Beta minus decay (1) Beta minus decay: When a neutron of a decaying isotope breaks into electron, antineutrino, and a proton. atomic mass does not change, while atomic number goes up by oneProton stays in nucleus. So, atomic mass does not change, while atomic number goes up by one.

11. Beta plus decay (2) Beta plus decay: When a proton of a decaying isotope breaks into a positron (= antiparticle of an electron), a neutrino, and a neutron. atomic mass does not change, while atomic number goes down by one.Neutron stays in nucleus. So, atomic mass does not change, while atomic number goes down by one. Beta particles can damage human body cells, but 2-3 cm thick wood is enough to protect you.

13. Gamma Decay High energy wavesHigh energy waves Called gamma radiation or gamma rays Does not change atomic mass or atomic numberDoes not change atomic mass or atomic number

14. Gamma Decay Energy released is the most penetrating and can pass through human body causing severe damage. wall of leadA big wall of lead is needed to protect you.

16. Half-Life Not all atoms of a radioactive isotope decay at once. The time it takes for ½ of the atoms to change can be measured. It is called half-life. This is useful in determining the ages of rocks and fossils in a process known as radioactive dating.