Chapter 3 - Radioactivity
Henri Becquerel discovered that uranium salts emit radiation.
Marie Curie discovered the radioactive elements radium and polonium.
Radioactivity is the spontaneous breaking up of certain unstable nuclei, accompanied by the emission of radiation.
There are 3 types:
alpha particles: + charge
beta particles: - charge
gamma rays: neutral
Alpha particles are helium nuclei, with a positive charge and little penetrating ability.
Beta particles are electrons, with a negative charge and greater penetrating ability than alpha particles.
Gamma rays are high energy electromagnetic, with greater penetrating ability than beta particles.
A Geiger-Muller tube detects radioactivity.
| Chemical Reaction | Nuclear Reaction |
|---|---|
| Changes in distribution of electrons. | Changes in the number of protons and neutrons (except with gamma rays) |
| Bonds break and new bonds form. | No bonds broken or formed. |
| No new elements formed. | New elements form (except with gamma rays) |
\n The half-life of a radioactive isotope is the time taken for half of the atoms in a sample of the isotope to decay.
Applications of Radioactivity:
- Cobalt-60 is used in food preservation by irradiation. The gamma rays kill micro-organisms and insects present in the food that could cause the food to go off.
- Cobalt-60 is used in the treatment of cancer by radiation.
- Carbon dating is used in archaeology to estimate the age of objects. Living things contain carbon-14 and carbon-12 in the same ratio as present in air.
Equation for the decay of C-14: C-14 → N-14 + β−