1. 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

2. 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.

3. 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

4. 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.

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

6. 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).

7. 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.

8. 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.

9. 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.

10. Types of Radiation:
Alpha radiation
Beta radiation
Gamma radiation

11. 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

12. 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.

13. Alpha (α) Radiation U Th + He Example: Alpha decay of Uranium-238 23892
Radioactive decay Th
234 90 + He 4 2
U-283 is used in geological dating (uncovering the age of rocks)

14. 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

15. 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

16. 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.

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

18. 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 + +

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