Section 19.1 Radioactivity TYPES OF RADIOACTIVE DECAY EQ.: WHAT ARE THE DIFFERENT TYPES OF RADIOACTIVE DECAY AND HOW ARE THESE REPRESENTED IN A NUCLEAR EQUATION?

Section 19.1 Radioactivity What do we mean by Radioactivity? Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. An unstable nucleus releases energy to become more stable

Section 19.1 Radioactivity nucleons – particles found in the nucleus of an atom –neutrons –protons atomic number (Z) – number of protons in the nucleus mass number (A) – sum of the number of protons and neutrons isotopes – atoms of the same element (identical atomic numbers) but different number of neutrons (different mass numbers) A Review of Atomic Terms

Section 19.1 Radioactivity A. Radioactive Decay radioactive – nucleus which spontaneously decomposes forming a different nucleus and producing one or more particles nuclear equation – shows the radioactive decomposition of an element

Section 19.1 Radioactivity Radioactive decay results in the emission of either : an alpha particle (  ), a beta particle (  ), or a gamma ray  Radioactive Decay or positron emmission or electron capture

Section 19.1 Radioactivity BAND OF STABILITY

Section 19.1 Radioactivity ALPHA DECAY Atoms with more than 83 protons are radioactive and decay spontaneously. Number of neutrons and protons needs to be reduced to make these elements more stable. Alpha-particle production Alpha particle – Helium nucleus

Section 19.1 Radioactivity ALPHA DECAY Product has atomic number lower by 2 and mass number lower by 4 EXAMPLES ALWAYS THIS PARTICLE IN ALPHA DECAY!!!

Section 19.1 Radioactivity Alpha Decay Ra Rn He 4 2

Section 19.1 Radioactivity Alpha Decay What particle is formed when polonium-210 undergoes alpha decay?

Section 19.1 Radioactivity BETA DECAY Atoms with too many neutrons relative to the number of protons undergo beta decay. Example: C 14 6 Neutron-to-proton ratio is 1.33 : 1 Unstable 12 6 C Neutron-to-proton ratio is 1 : 1 Stable

Section 19.1 Radioactivity A. Types of Radioactive Decay Beta-particle production Beta Decay Fast moving e - emitted from an unstable nucleus 0: Insignificant mass of e - compared to mass of nucleus -1: Negative charge of particle 14 6 C 14 7 N + 0 β 0 e) ( same as Mass number is the same as original but atomic number increases by 1

Section 19.1 Radioactivity A. Types of Radioactive Decay EXAMPLES Beta Decay Mass number is the same as original but atomic number increases by 1

Section 19.1 Radioactivity Beta Decay The atomic number, Z, increases by 1 and the mass number, A, stays the same.

Section 19.1 Radioactivity Beta Decay Po  0 At

Section 19.1 Radioactivity A. Radioactive Decay Gamma ray release Gamma Emission Net effect is no change in mass number or atomic number. Gamma ray – high energy photon –Examples

Section 19.1 Radioactivity A. Types of Radioactive Decay Positron production POSITRON EMISSION (below the band of stability) Net effect is to change a proton to a neutron. Atomic number decreases by 1 and mass number is the same. Positron – particle with same mass as an electron but with a positive charge –Examples

Section 19.1 Radioactivity A. Types of Radioactive Decay An electron is captured from the lower energy orbitals. (first shell). e - combines with p + to form a n 0. Electron Capture (below the band of stability) –Example Net effect is to change a proton to a neutron. Atomic number decreases by 1 and mass number is the same. X-ray

Section 19.1 Radioactivity Kinds of Radioactivity The three main decays are Alpha, Beta and Gamma

Section 19.1 Radioactivity A. Radioactive Decay Decay series

Section 19.1 Radioactivity Early Pioneers in Radioactivity Roentgen: Discoverer of X- rays 1895 Becquerel: Discoverer of Radioactivity 1896 The Curies: Discoverers of Radium and Polonium Rutherford: Discoverer Alpha and Beta rays 1897

Section 19.1 Radioactivity A. Radioactive Decay

Section 19.1 Radioactivity B. Nuclear Transformations Nuclear transformation – change of one element to another Bombard elements with particles – Examples

Section 19.1 Radioactivity B. Nuclear Transformations Transuranium elements – elements with atomic numbers greater than 92 which have been synthesized

Section 19.1 Radioactivity C. Detection of Radioactivity and the Concept of Half- life Geiger-Muller counter – instrument which measures radioactive decay by registering the ions and electrons produced as a radioactive particle passes through a gas- filled chamber

Section 19.1 Radioactivity C. Detection of Radioactivity and the Concept of Half- life Scintillation counter – instrument which measures the rate of radioactive decay by sensing flashes of light that the radiation produces in the detector

Section 19.1 Radioactivity C. Detection of Radioactivity and the Concept of Half- life Half-life – time required for half of the original sample of radioactive nuclides to decay

Section 19.2 Application of Radioactivity 1.To learn how objects can be dated by radioactivity 2.To understand the use of radiotracers in medicine Objectives

Section 19.2 Application of Radioactivity A. Dating by Radioactivity Originated in 1940s by Willard Libby –Based on the radioactivity of carbon-14 Radiocarbon dating Used to date wood and artifacts

Section 19.2 Application of Radioactivity B. Medical Applications of Radioactivity Radioactive nuclides that can be introduced into organisms and traced for diagnostic purposes. Radiotracers

Section 19.3 Using the Nucleus as a Source of Energy 1.To introduce fusion and fission as sources of energy 2.To learn about nuclear fission 3.To understand how a nuclear reactor works 4.To learn about nuclear fusion 5.To see how radiation damages human tissue Objectives

Section 19.3 Using the Nucleus as a Source of Energy A. Nuclear Energy Two types of nuclear processes can produce energy –Combining 2 light nuclei to form a heavier nucleus - fusion –Splitting a heavy nucleus into 2 nuclei with smaller mass numbers - fission

Section 19.3 Using the Nucleus as a Source of Energy B. Nuclear Fission Releases 2.1  J/mol uranium-235 Each fission produces 3 neutrons

Section 19.3 Using the Nucleus as a Source of Energy B. Nuclear Fission Chain reaction – self sustaining fission process caused by the production of neutrons that proceed to split other nuclei Critical mass – mass of fissionable material required to produce a chain reaction

Section 19.3 Using the Nucleus as a Source of Energy B. Nuclear Fission

Section 19.3 Using the Nucleus as a Source of Energy C. Nuclear Reactors

Section 19.3 Using the Nucleus as a Source of Energy C. Nuclear Reactors Reactor core

Section 19.3 Using the Nucleus as a Source of Energy D. Nuclear Fusion Process of combining 2 light nuclei Produces more energy per mole than fusion Powers the stars and sun

Section 19.3 Using the Nucleus as a Source of Energy D. Nuclear Fusion Requires extremely high temperatures Currently not technically possible for us to use as an energy source

Section 19.3 Using the Nucleus as a Source of Energy E. Effects of Radiation Energy of the radiation Penetrating ability of the radiation Ionizing ability of the radiation Factors Determining Biological Effects of Radiation Chemical properties of the radiation source

Section 19.3 Using the Nucleus as a Source of Energy E. Effects of Radiation

Section 19.3 Using the Nucleus as a Source of Energy E. Effects of Radiation