In 1899, Ernest Rutherford discovered that uranium compounds produce three different kinds of radiation. He separated the radiations according to their penetrating abilities and named them a alpha, b beta, and g gamma radiation, after the first three letters of the Greek alphabet.
In alpha decay, the nucleus emits an alpha particle; an alpha particle is essentially a helium nucleus, so it is a group of two protons and two neutrons. A helium nucleus is very stable. Alpha radiation can be stopped by a sheet of paper.
A beta particle is an electron. In beta decay an electron is involved. The number of neutrons in the nucleus decreases by one and the number of protons increases by one. Six millimeters of aluminum are needed to stop most beta particles
The third class of radioactive decay is gamma decay, in which the nucleus changes from a higher-level energy state to a lower level. Several millimeters of lead are needed to stop gamma rays.
Halflife of a Radioisotope
The purpose of this experiment is to determine the halflife of a radioisotope. Halflife is defined as the time it takes for one half of the atoms in a radioactive sample to decay. Data will be collected on the activity of a radioactive isotope vs. elapsed time. The halflife will then be determined by two different types of graphical analysis.
Radioactive Decay of Candium
Some naturally occurring isotopes of elements are not stable. They slowly decompose by discarding part of the nucleus. The isotope is said to be radioactive. This nuclear decomposition is called nuclear decay. The length of time required for half of the isotope to decay is the substance's half-life. Each radioactive isotope has its own particular half-life. However, when the amount of remaining isotope is plotted against time, the resulting curve for every radioisotope has the same general shape.
( Sumber Rujukan Sains Anda )