Unit: Nuclear Chemistry Day 1 – Notes Unit: Nuclear Chemistry Introduction to Nuclear Radiation Pictures starting from upper right moving left: Radioactivity symbol, particle accelerator, mushroom cloud (nuclear explosion), Marie and Pierre Curie, cooling tower of nuclear power plant

After today you will be able to… Explain how an unstable nucleus releases energy. Differentiate between chemical and nuclear reactions. Identify the three types of nuclear radiation and their properties.

A quick review… Isotope: Atoms of the same element (same atomic number) with different numbers of neutrons (different mass numbers). Examples: Carbon-12, Carbon-13

A quick review… Atomic number: The number of protons in a nucleus. This cannot change during chemical reactions. Mass number: The number of protons + neutrons in the nucleus of an atom.

A quick review… A shorthand way of indicating the mass number and atomic number for an atom: C 12 Mass number 6 Atomic number

Radioactivity Was first observed by Marie and Pierre Curie (1900s) using uranium (U) atoms. Radioactivity: The process by which substances spontaneously emit rays and particles (radiation).

Radioactivity differs from chemical reactions in a number of ways: In chemical reactions, atoms attain a stable electron configuration by losing/sharing electrons. In nuclear reactions, the nucleus of an unstable isotope gains stability by undergoing changes.

Radioactivity differs from chemical reactions in a number of ways: Unlike chemical reactions, nuclear reactions are not affected by changes in temperature, pressure, or the presence of catalysts. Nuclear reactions of an isotope cannot be sped up, slowed down, or turned off.

Radioactivity Unstable radioactive isotopes (radioisotopes) are transformed into stable (nonradioactive) isotopes of a different element. Radioactive decay: is the process by which an unstable nucleus emits radiation and energy in order to obtain a more stable state.

Types of Radiation: Alpha radiation Beta radiation Gamma radiation

Alpha (α) Radiation Recall, Rutherford used alpha particles to discover the nucleus in his Gold Foil Experiment. Consists of helium nuclei that has been emitted from a radioactive source. Contains two protons, two neutrons, and has a positive two charge. Usually written as: He or α (the electric charge is usually omitted). 4 2

Alpha (α) Radiation Due to its large mass and charge, alpha particles do not travel very far. They cannot penetrate very well – a sheet of paper or the surface of your skin stops them. However, they are toxic when ingested.

Alpha (α) Radiation U Th + He Example: Alpha decay of Uranium-238 238 92 Radioactive decay Th 234 90 + He 4 2 U-283 is used in geological dating (uncovering the age of rocks)

Beta (β) Radiation Results from the breaking apart of a neutron into a proton and an electron (beta particle). Usually written as: e or β Has much less mass than an alpha particle and can therefore penetrate more easily. Can pass through paper, but is stopped by foil or wood. -1

Beta (β) Radiation C N + e Example: Beta decay of Carbon-14 14 6 Radioactive decay N 14 7 + e -1 C-14 is used in determining the age of organic matter

Gamma (γ) Radiation A high energy photon emitted by a radioisotope. Usually written as: γ or γ Often emitted with alpha or beta particles during radioactive decay. Has no mass or charge. Extremely penetrating and can be very dangerous.

Gamma (γ) Radiation Easily passes through paper, wood, and the human body. Penetration can be stopped, although not completely, by several centimeters of lead.

Gamma (γ) Radiation γ Th Rn He + + Example: Gamma/alpha emission from Thorium-230 γ Th 230 90 Radioactive decay Rn 226 88 He 4 2 + +

Questions? Complete the “Learned” portion of your table from the bellwork today. Then hand it in!