Following the somewhat serendipitous discovery of radioactivity by Becquerel, many prominent scientists began to investigate this new, intriguing phenomenon. During the beginning of the twentieth century, many radioactive substances were discovered, the properties of radiation were investigated and quantified, and a solid understanding of radiation and nuclear decay was developed. The spontaneous change of an unstable nuclide into another is radioactive decay. The unstable nuclide is called the parent nuclide ; the nuclide that results from the decay is known as the daughter nuclide. The daughter nuclide may be stable, or it may decay itself. The radiation produced during radioactive decay is such that the daughter nuclide lies closer to the band of stability than the parent nuclide, so the location of a nuclide relative to the band of stability can serve as a guide to the kind of decay it will undergo Figure 1.
An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid , liquid , gas , and plasma is composed of neutral or ionized atoms. They are so small that accurately predicting their behavior using classical physics —as if they were tennis balls, for example—is not possible due to quantum effects. Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons.
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The writers originally intended many of these characters as one-time jokes or for fulfilling needed functions in the town. A number of them have gained expanded roles and have subsequently starred in their own episodes. According to the creator of The Simpsons , Matt Groening , the show adopted the concept of a large supporting cast from the Canadian sketch comedy show Second City Television. Agnes Skinner voiced by Tress MacNeille  is the mother of Principal Skinner and first appeared in the first season episode " The Crepes of Wrath " as an old woman who embarrassingly calls her son "Spanky". However, as episodes progressed, the character turned bitter.