Lesson 2: Radioactivity

Laws of Physics

The ______ allow certain combinations of protons and neutrons in the nucleus to co-exist in a state of peaceful tranquility

Radioactive

As a result, these elements exhibit a degree of nuclear instability which manifests itself as _____.

Radioisotopes

Isotopes which spontaneously emit radiation are called _____

Radioactive Decay

Is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. 

Radioactive Decay

The general idea is that an unstable nucleus releases energy to become stable. 

Transmutation

Changing from one element to another after decaying 

Antoine Henri Becquerel

he discovered by accident that uranium can blacken a photographic plate, even in the dark 

1896

When did Antoine Henri becquerel discover that Uranium can blacken a plate?

Antoine Henri Becquerel

He studied phosphorescence and used uranium for glass utensils and cups. 

Phosphorescence

What did Antoine Henri Becquerel study?

Marie and Pierre Curie

Studied intensively the uranium and discovered other natural radioactive elements such as radium or polonium

3.7 x10^10 Decay/s or DPS 

According to Marie Curie, the activity of 1g Ra = 1Ci =

1 DCP

1Bq =

Polonium

named after Marie Curie’s homeland, Poland.) 

1911 Nobel Prize in Chemistry

She received the 1911 Nobel Prize in Chemistry after separating pure radium 

Aplastic Anemia

marie died from

Cosmic Background Radiation

Terrestrial Radiation

Internal Radionuclide

3 Sources of Radiation

Anisotropies

Small variations in temperature of the background radiation from point to point on the sky are called

Cosmic Background Radiation

Leftover heat from the Big Bang 

Terrestrial Radiation

Radioactive material is also found throughout nature such as in soil, water and vegetation 

Thorium Radium Radon

decay products of uranium

Uranium 238 and Thorium 232

produces Radon Gas

Potassium 40

found in bananas

Radon gas

Is a naturally occurring radioactive gas which can accumulate in enclosed places, including houses and other buildings

Potassium 40 Carbon 14 Lead 210

Internal Radionuclides

Potassliim 40

It is the primary source of radiation from the human body, with a concentration fairly high. 

Carbon 14

Radiocarbon dating

Sources of ___ essentially are from human food derived from plants 

Radon 22

accumulate in lung tissues 

Medical Procedures Consumer Products Nuclear Fuel Cycle Residual Fallout

Man-Made Radiation Sources

Members of the Public Occupationally Exposed Individuals

2 groups eexposed to man made radiation sources

Occupational dose

the dose received by an individual in the course of employment in which the individual’s assigned duties involve exposure to radiation or to radioactive material.

Dosimeter

Occupationally exposed individuals are monitored for radiation exposure with

Iodine 131

Scanning Thyroid

Technetium 99m

Nuke med and gamma camera

Cobalt 60

Radiation Therapy Machine

Cesium 137 and Americium 241

Brachytherapy and Teletherapy

2.7 x10-11 Ci

1 Bq =

Doramad

Radioactive toothpaste

Iiquid Sunshine

bottled water laced with radium,

1953

radium-based contraceptive jelly.

1952 Life magazine

Radon gas in mines

Department of Commerce Information Circular

the radium paint might contain from 0.7 to 3 and even 4 milligrams of radium. 

Radium Girls

The girls who paintedwatches with radium

Half Life

 the time required for the disintegration of one half of the radioactive atoms that are present when measurement starts. 

Physical Half Life Biological Half Life Effective Half Life

Types of half-life

Physical Half Life

Defined as the period of time required to reduce that radioactivity level of  a source to exactly one half its original value.

Biological Half Life

The time the body takes to eliminate one half the amount of radioactive atom (biological elimination: pee, stool)

Effective Half Life

Period of time required to reduce the radioactivity level of the whole body to exactly one half its original value due to both biological elimination and decay 

Radioactive Decay

The radioactive/radionuclide transforms into different nuclides during the disintegration or radiation emission. 

Decay Chain

Is a sequence of unstable atomic nuclei and their modes of decays which leads to a stable nucleus 

Alpha Decay Beta Decay (Beta Plus Beta Minus) Gamma Emission Electron Capture

Modes of Decay

Alpha Decay

A radionuclide emits an ALPHA PARTICLE consisting of 2 neutrons and 2 protons 

Discrete energy (4 & 7 MeV) 

Short range (<0.1mm)

Specific ionization (40,000 ion pair/cm)

Properties of an Alpha Particle

Atomic number is more than 82 and Mass Number is more than 150

Conditions if an Alpha Particle

Beta Minus Decay

A radionuclide converts a neutron into a proton.

Beta Minus Decay

The excess energy is released as a NEGATRON & ANTI-NEUTRINO 

Negatron and Anti-Neutrino

The teo ejected particles of Beta Minus Decay

Positron and Neutrino

Particles ejected by Beta Plus Decay

Anti-Neutrino

the neutron turned into proton              

Beta Minus Decay

• Too many Neutrons 

• Too few Protons

Beta Plus Decay

Too may Protons

Too few Neutrons

Beta Plus Decay

A radionuclide converts a proton into a neutron. The excess energy is released as a POSITRON & NEUTRINO 

Electron Capture

A radionuclide converts a proton into a neutron by capturing its own electron resulting to the release of characteristic X-rays and Auger Electrons 

Gamma Decay

A radionuclide in its excited state excites by emission of one or more HIGH FREQUENCY PHOTON

Gamma Decay

High energy state atom