1. Scientists in the late 1800s determined that there were different types of radiation in addition to visible light. Some types of radiation have mass, some do not. Some types of radiation are electrically positive, some are negative or neutral. Cathode rays were found to be made up of electrons by Sir J.J. Thomson in 1897. Cathode ray tubes were the basis of the television until LCD and plasma screens. X-rays were discovered by Wilhelm Röntgen in 1895 and were found to be part of the electromagnetic spectrum. Henri Becquerel and Marie and Pierre Curie were the pioneer scientists of radioactive elements. Marie Curie coined the term radioactivity for the spontaneous emission of radiation from the nucleus of an atom. Radioactivity and its History 10.1 VOCABULARY radioactivity

2. All atoms are made of subatomic particles. All atoms of an element have the same chemical properties, although the atoms of an element can have different masses. Atoms of the same element with different masses are called isotopes of that element. An isotope of an element has the same atomic number, but a different mass number. This means that they have the same number of protons, but a different number of neutrons. Radioactivity and the Nucleus 10.2 VOCABULARY nucleus proton neutrons isotopes

3. Isotopes can be written in standard atomic notation. For example:uranium-238 carbon-12 Radioactivity and the Nucleus 10.2 VOCABULARY nucleus proton neutrons isotopes

4. An unstable nucleus that emits radiation is undergoing radioactive decay. Transmutation changes a parent nucleus into a daughter nucleus. Radioactive atoms emit radiation of three different types: 1. alpha radiation 2. beta radiation 3. gamma radiation Alpha, beta, and gamma radiation have different properties of mass, charge, penetrating ability, and reaction to electric and magnetic charges. Radioactive Decay 10.3 VOCABULARY radioactive decay parent nucleus daughter nucleus alpha particle beta particle gamma ray

5. The rate of radioactive decay of a sample is not affected by physical or chemical changes such as temperature, pressure, or age of the sample. The rate of decay of a radioactive sample is predictable. Half-Life 10.4 VOCABULARY half-life decay series

6. The average length of time for half of the parent nuclei in a sample to decay is called the half-life. It is a constant number for a given isotope. The half-life of a radioactive isotope can be determined from graphs of number of parent nuclei versus time and activity level versus time. Radioactive isotopes can be used to determine the age of some materials. Carbon-14 has a half-life of 5730 years and is useful for radioactive dating of material that was once living. Half-Life 10.4 VOCABULARY half-life decay series

7. Radioactivity and the Atom All atoms are made of subatomic particles: protons, neutrons, and electrons Atoms of a single element that differ in mass are called isotopes. Isotopes have the same number of protons but vary in the number of neutrons. The isotopes of some elements are radioactive. For example uranium-238 and carbon-14. 10 CHAPTER

8. Radioactivity and the Atom Radioactive atoms undergo radioactive decay, which can be written as nuclear reaction equations. There are three basic types of radioactive decay: alpha decay, beta decay, and gamma decay. The rate of decay of a radioactive sample is predictable and is described by the half-life of the radioactive isotope. 10 CHAPTER

9. Radioactivity and the Atom Activity Create a mind map with “RADIATION” in the centre. Create branches showing all the different types of radiation you can think of. Branch out further describing the uses of these types of radiation in everyday life (as many as you know). Read 10.1 (pages 275–278) for a better understanding of the different forms of radiation and their uses. 10 CHAPTER Type Uses Type RADIATION

10. Radioactivity and the Atom 10 Key Ideas Atoms of a single element that differ in mass are called isotopes. The atoms of some elements are radioactive, which means that they undergo radioactive decay. There are three basic types of radioactive decay and these processes can be written as nuclear reaction equations. The rate of decay of a radioactive sample is predictable and is described by the half-life of the radioactive isotope. CHAPTER