NUCLEAR CHEMISTRY

 Welcome to Master Segun's class!

In today’s class, we will be talking about nuclear chemistry. Enjoy the class!

TOPIC: NUCLEAR CHEMISTRY

CONTENT

1. Types and Nature of Radiation

2. Half-life as a measure of the stability of the nucleus.

NUCLEAR CHEMISTRY is an aspect of chemistry that deals with nuclei of atoms.

RADIOACTIVITY 

This is the spontaneous emission of radiation by a radioactive element such as Thorium, Uranium etc.

CHARACTERISTICS 

1. Spontaneously and continually emitting of radiation by a radioactive element

2. Temperature and pressure do not affect radioactivity

3. The radiation can pass through opaque objects

4. It affects photographic plates

5. It causes ionization of gases through which it passes.

6. It causes fluorescence of certain substance

7. It releases a large amount of energy.

TYPES OF RADIATIONS 

There are three (3) types of radiation

1. Alpha ά, 

2. Beta, β

3. Gamma, Y

The diagram shows how alpha, beta and gamma radiation would be deflected by a magnetic field acting perpendicular to the path of the particles.

Alpha particles are deflected a little because of their large mass while beta particles are deflected much more because they are nearly two thousand times lighter. They have a negative charge while alpha particles are positive and so they are deflected in the opposite direction.

Notice that the gamma rays are not deflected at all – this is because they have no charge.

In the diagram the magnetic field acts into the plane of the paper.

CHARACTERISTICS OF ALPHA-RAYS

1. They are Helium in nature 42He with 4 atomic mass and 2 atomic number

2. Alpha rays are fast-moving streams of positively charges

3. They are deflected toward the negative plate in an electrostatic field

4. They have a very low penetrating power

5. They can be absorbed/stopped by a thin sheet of paper on Aluminium foil

6. They cause fluorescence of some materials e.g Zinc Sulphide

CHARACTERISTICS OF BETA-RAYS

1. They are electron in nature with a mass number of zero and charge of -1

2. They are a fast-moving stream of electrons

3. They can penetrate than alpha rays

EVALUATION 

1. State two (2) properties of ά, β, and Y rays each.

2. What do you know about radioactivity?

Detection of radiation

THE RADIATION CAN BE DETECTED BY USING THE FOLLOWING DEVICES 

1. Geiger Miller Counts

2. Scintillation counter

3. Diffusion cloud chamber

HALF-LIFE 

The half-life of a radioactive element is the time taken for half of the actual number of atoms in a given substance or radioactive element to decay.

NUCLEAR STABILITY 

The spontaneous disintegration/decay of the nucleus of an element is due to its instability.

The NEUTRON-PROTON RATIO determines the stability of an element.

This varies between unity for the lighter elements and a value of about 1.5 for the heavier element with atomic numbers around eighty.

N.B. Atoms with a neutron – protons less than 1 or greater than 1.5 tends to be unstable.

EVALUATION 

1. State two methods through which radiation can be detected.

2. What is half-life as a measure of the stability of the nucleus?

GENERAL EVALUATION 

1. Define the term nuclear chemistry

2. Define the term radioactivity.

3. Explain the term radioisotopes

4. Give an account of the uses of radioisotopes.

READING ASSIGNMENT 

New School Chemistry by O.Y, Ababio pages 299-304.

WEEKEND ASSIGNMENT 

1. ____ is an example of radiation (a) Aloha (b) Carbon (c) Uranium (d) Nucleus.

2. Alpha particle was deflected towards negative plate while Beta deflected toward (a) 3. Neutral plate (b) Negative plate (c) Zero plate (d) positive plate

4. The following caused fluorescence of matter except for (a) Alpha (b) Beta (c) Gamma (d) X-ray

THEORY 

1. Find the half-life of a radioisotope element which was found to be 120g initially and later changed to 15g in 24 hours

2. State the three main type of radiation with their properties each.