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

Radiation Survey

Annual Radiation Survey