Radioactivity Chapter 4: Section 1. Discovering Radioactivity Henri Becquerel hypothesized that...
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Transcript of Radioactivity Chapter 4: Section 1. Discovering Radioactivity Henri Becquerel hypothesized that...
Radioactivity
Chapter 4: Section 1
Discovering Radioactivity
Henri Becquerel hypothesized that fluorescent minerals give off X rays
Unexpected Result
• Review Page 88 to answer the following question in your notes:• How did Becquerel
discover that energy comes from Uranium, an element in the mineral?
Naming the unexpected Nuclear Radiation: high energy particles and rays that are emitted by the nuclei Radioactivity: the process by which an unstable nucleus gives off nuclear radiation
Kinds of Radioactivity
Alpha Decay
1) Alpha () – an atom decays into a new atom and emits an alpha particle
2) 2 protons and 2 neutrons – the nucleus of a helium atom
3) Mass= 4 Charge= + 2
Unstable nucleus
New nucleus Alpha particle
Alpha Decay
Example: Radium-226
Conservation of Decay
Look at example on page 89
Mass number is conserved.
Charge is conserved
Beta Decay
Beta () – an atom decays into a new atom by changing a neutron into a positron or a electron. Charge= -1 or +1Mass= 0
Unstable nucleus
Beta particle
Two Types of Beta Decay
Carbon 14
Two Types of Beta Decay An isotope is an atom with a different number of neutrons:
Notice that the mass number is different. How many neutrons does each isotope have?
Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more.
Gamma Decay
1) Gamma – after or decay surplus energy is sometimes emitted.
2) Occurs when particles of a nucleus shift3) The atom is not changed. No mass or
charge
Unstable nucleus New nucleus
Gamma radiation
Penetrating Power of Radiation
Damage to Matter
When an organism absorbs radiation, its cells can be damaged• Radiation sickness• Fatigue and Loss of appetite• Hair loss• DeathCancerRadiation can also damage non-living matter
Uses of Radioactivity
• Isotopes are used to determine the age of objects
• Smoke detectors• Tracers: radioactive elements whose
paths cane be followed through a process or reaction
Radioactivity in real life
• Doctors use tracers to help diagnose problems• They have short half-lives and are fed
or injected into patient• Follow it as it travels through the body
• Isotopes can detect defects in structures• Radiation is used to detect thickness
in metals