Types of Radiation and Unstable Nuclei

1. Types of Radiation and Unstable Nuclei

2. I. Chemical and Nuclear Reactions • Chemical reactions only involve an atom’s electrons • Nuclear reactions involve changing an atom’s nucleus • Nuclear reactions release a million times more energy than chemical reactions • Unlike chemical reaction, nuclear reactions are not affected by temperature, pressure, or a catalyst.

3. II. Nuclear Vocabulary • Radioactivity – the process of emitting radiation. • Radiation - rays and particles emitted by a radioactive source. • Radioisotopes – isotopes of atoms with unstable nuclei and emit radiation to obtain a more stable nuclei • Radioactive decay - Unstable nuclei losing energy by emitting radiation in a spontaneous process. • Nucleon – refers to both protons and neutrons

4. III. Which Isotopes are Radioactive? • Small Nuclei - Atoms which contain up to 20 protons (up to Calcium) are usually stable. • Large Nuclei - Larger nuclei tend to be radioactive. All nuclei with 84 or more protons (Polonium and up) are radioactive. For example, all isotopes of Uranium are radioactive. • Atoms with more neutrons than protons - There are radioactive nuclei that have less than 84 protons. These nuclei have more neutrons than protons. For example, Carbon-12 (6 protons and 6 neutrons) is stable, while Carbon-14 (6 protons and 8neutrons) is radioactive.

5. IV. Why Does an Atom Undergo Radioactive Decay? • Radioactive atoms emit radiation because their nuclei are unstable. • The stability of the nucleus depends on the neutron to proton ratio • Neutrons vs. protons graph stable nuclei found in a region called the band of stability.

6. V. Types of Radiation – Alpha Radiation • Alpha radiation are attracted to the negatively charged plate • Alpha particles contain two protons and two neutrons (A helium nucleus) • Blocked by paper • Least penetrating form of radiation (only travels a few centimeter in the air) • Carry +2 charge • Symbolized by He or  4 2 4 2

7. VI. Types of Radiation – Beta Radiation • Beta radiation attracted to the positively charged plate • Carry –1 charge • Beta particles are fast moving electrons • Blocked by metal foil or wood • Medium penetration power (travels a few meters in the air) • Symbolized by e or  0 -1 0 -1

8. VII. Types of Radiation – Gamma rays • Gamma rays are high energy radiation that possess no mass. • Possess no electrical charge and are not deflected by magnetic or electrical fields. • Not completely blocked by lead or concrete • The most penetrating and damaging type of radiation • Carry no charge • Symbolized by  0 0

11. IX. Electrostatic Force • Electrostatic force is when like charges repel and opposite charges attract.

12. X. Strong Nuclear Force • The strong nuclear force or nuclear force is an attractive force that acts between all nuclear particles that are extremely close together. • It keeps the nucleus together.

13. Remember Mass Number and Atomic Number C 14 6 Mass number Atomic number

14. XI. Writing and Balancing Nuclear Equations • In a balanced nuclear equation, mass numbers and atomic numbers are conserved. Example • Th  Ra + He • Notice the mass numbers and atomic numbers add up to the same on both sides of the equation 226 88 4 2 230 90

15. VIII. Electron Capture • Electron capture occurs when a nucleus of an atom draws in an electron. • Rb + e → Kr • Also known as Beta capture 81 37 0 - 1 81 36

16. Practice • Zr e + ? • Po  He + ? • ?  Rn + He • Ca  e + ? • Cm  He + ? 97 40 0 -1 97 41 Nb 218 84 4 2 214 82 Pb 222 86 4 2 226 88 Ra 0 -1 47 21 47 20 Sc 240 94 Pu 244 96 4 2