INDUCED RADIOACTIVITY science for 8 to 12

The phenomenon by which radioactivity is induced in an element, is called induced radioactivity or artificial radioactivity.

When a stable nucleus is bombarded with a high energy particle, it gets changed into another which is often radioactive. For example, when aluminum is bombarded by a (alpha) particles, it produces radio-phosphorus.

15P30 which is radioactive with a half life about 3 minutes, decays to a stable isotope of silicon by emitting a positron (positive electron) which has the same mass as electron, but positive charge.

Curie Joliot and her husband Frederick. Joliot were the first to discover induced radioactivity in 1934. They were awarded 1934. Nobel prize in chemistry. They bombarded elements aluminium and boron with a particles. They observed that the targets continued to emit radiations even after the removal of the a source. The radiations consisted of positrons.

Radioactivity elements radiations isotopes for std 8 to 10

REVIEW
You have learnt the following earlier, recall them.
An atom is made up of three fundamental particles namely proton, neutron and electron.
Protons and neutrons are bound together is the central part of an atom, called the nucleus.
Electrons revolve round the nucleus in different imaginary orbits.
The number of protons in an atom is called its atomic number, represented by Z.
Protons and neutrons is a nucleus have a common name ‘nucleons’ the total number of nucleons in an atom is known as the atomic mass number represented by A. Mass number is very close to the atomic mass.
Electron (-1eo) is a negatively charged particle with negligible mass.
Proton (+1p1) is a positively charged particle with unit mass considering the mass of hydrogen atom to be ‘one unit’.
Neutron (0N1) is an electrically neutral particle with unit mass.

INTRODUCTION 

In 1896, Henri Becquerel (1852-1908) a French scientist, accidentally discovered radioactivity. He found that a photographic plate, wrapped well to protect is from visible light, was blackened by a mineral containing uranium. He concluded that the mineral emitted a new kind of radiations which occurred without any external cause. The emission of these radiations is not affected by external factors like temperature, pressure, electric field and magnetic field. The radiations were called Becquerel rays.

Radioactivity 

All elements which emit Becquerel rays are said to be radioactive and the elements are called radioactive elements.
All the elements from atomic number 81 to 92 are found to be radioactive. Experiments show that atoms of radioactive elements disintegrate into atoms of other elements. It became clear that the radiations must emanate from the nucleus and radioactivity is a nucler phenomenon. We can conclude that the phenomenon is due to disintegration of an ustable nucleus accompanied by some type of radiation.
The property of spontaneous disintegration of certain unstable. This is referred to as natural radioactivity. Radioactivity produced artificially or induced, is called artificial or induced radioactivity. The radiations emitted by radioactive elements are called radioactive radiations.
In 1898, Marie Curie (1867-1934) and her husband Pierre Cune (1959-1906) discovered a new element named Polonium and later on, another element named Radium, In 1903 Nobel prize in physics was shared by H. Becquerel, M. Curie and P. Curie, for their discovery of radioactivity. In 1911, M. Curie was awarded Nobel prize in chemistry for the extraction of radium in its purest form.