Fig
6Radioactivity
Radio activity was discovered in 1896 by Henri Becquerel while he was working with compounds that contained uranium. Photographic plates that were used to keep out light because partially exposed when they were brought near any of the compounds that were part uranium. He speculated that the exposure was caused by some form of ray passing through the plates. He also found the some materials other than uranium contained these rays. These materials are said to be radio active. There are three kinds of radiation known as α alpha, β beta, and γ gamma radiation. These were discovered by Enrest Rutherford in 1899. Alpha particles are the nucleus of the He atom, beta particles are high speed electrons and gamma rays are high energy photons.
α
Alpha decay is the emission of an He nucleus. Because the alpha particles contain protons and neutrons, then they must come from the nucleus of an atom. After undergoing alpha decay, the nucleus of the atom has gone through trans mutation which is the process of one element changing into another through the process of radioactive decay. So after going through alpha decay, the charge and mass of the nucleus has changed, changing the the element itself.
Fig
6
β
Beta particles are the negatively charged electrons that are emitted by the nucleus of an atom. Atoms that undergo beta decay do not experience mass changes because the mass of an electron is only a small portion of the atomic mass unit. Because of this, the mass of the nucleus that experiences beta decay only changes by a miniscule amount. Beta decay occurs when neutron changes into a proton. When this happens the number of protons changes which in turn changes the atomic number.
Fig
7
γ
Gamma rays are different from alpha and beta decay because they are a type of electromagnetic radiation. Gamma rays are high energy photons. They are similar to visible photons emitted by a light bulb but the wavelength is much shorter. Because of this they have a much higher energy level. The gamma rays are emitted when an atom undergoes a change in the arrangement of the protons and neutrons within the nucleus. The mass number and atomic number do not change when a nucleus emits a gamma ray.
Fig
8