Ministry of Education youth and sports of Ukraine

Chernivtsi National University named Yuri Fedkovych

Chemical Faculty

Department of Inorganic Chemistry

Term paper on the topic:

"Radioactivity. Families of radioactive elements"

Fulfilled second-year student

202 groups

Shevchenko Victoria

Supervisor: Korov'yanko О.О.

Chernivtsi 2012

Content:

Introduction

1. Radioactivity

1.1. Alpha radioactivity

1.2. Alpha barrier penetration

1.3. Alpha binding energy

1.4. Alpha, beta and gamma

1.5. Penetration of matter

2. Radioactive decay

3. Radioactive series

3.1. Thorium series

3.2. Neptunium series

3.3. Radium series

3.4. Actinium series

4. Radioisotope dating

5. Uses of radioactivity

6. Literature

Introduction

Radioactivity is the process whereby unstable atomic nuclei release energetic subatomic particles. The word radioactivity is also used to refer to the subatomic particles themselves. This phenomenon is observed in the heavy elements, like uranium, and unstable isotopes, like carbon-14.

Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, after which the SI unit for radiation, the Becquerel, is named. Becquerel discovered that uranium salts were able to blacken a photographic plate placed in the dark, even through a paper barrier. Subsequent experiments distinguished three distinct types of radiation -- alpha particles, beta particles, and gamma rays. These are positively charged, negatively charged, and neutral, respectively. In the United States, human exposure to radioactivity is measured in rads, where one rad represents 0.01 joule of energy absorbed per kilogram of tissue.

Radioactivity is a random process, meaning that it is physically impossible to predict whether or not a given atomic nucleus will decay and emit radiation at any given moment. Rather, radioactivity is quantified using half-life, which is the period of time it takes for half of the given nuclei to decay. Half-life applies to a sample of any size, from a microscopic quantity to all the atoms of that type in the universe. Half-life varies widely, from a couple seconds (Astatine-218) to billions of years (Uranium-238).

1. Radioactivity

Fig. 1. radioactivity

Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability. Because the nucleus experiences the intense conflict between the two strongest forces in nature, it should not be surprising that there are many nuclear isotopes which are unstable and emit some kind of radiation. The most common types of radiation are called alpha, beta, and gamma radiation, but there are several other varieties of radioactive decay.

Radioactive decay rates are normally stated in terms of their half-lives, and the half-life of a given nuclear species is related to its radiation risk. The different types of radioactivity lead to different decay paths which transmute the nuclei into other chemical elements. Examining the amounts of the decay products makes possible radioactive dating.

Radiation from nuclear sources is distributed equally in all directions, obeying the inverse square law. [1]