Periodic Table Essays - Chemistry, Nature, Periodic Table

Periodic Table Periodic Table First noticed by Greek people in about 400BC. They used the words element, and atom to describe the differences and smallest parts of matter. Those ideas lasted for 2000 years. Elements were Earth, Fire, Air, and Water that explained world stuff easily came and went. In the 1600s Boyle, an experimenter, influenced by Democritus, Gassendi, and Descartes lent important weight to the atomic theory of matter. In the 1700s Lavoisier divided the elements into four classes. John Dalton suggested that the mass of an atom is the important property. The chemical elements are composed of... indivisible particles of matter, called atoms... atoms of the same element are identical in all respects, particularly weight. n the 1800s Doereiner said that some elements had a relative atomic mass, and DeChancourtois made a table of elements to show the periodic reoccurrence of properties. In the 1860s Newland made a table of elements giving them a serial number in order of their atomic weighs starting with Hydrogen. Meyer and Mendeleyev made periodic tables independently. Meyer made it more periodicity of physical properties, and Mendeleyev made it more on the chemical properties. Mendeleyev published his periodic table & law in 1869. Periodic tables have always been related to how scientists thought about the shape and structure of the atom. Later, the table was reordered by Mosely according to atomic numbers(nuclear charge) instead of weight. Harry D. Hubbard, of the United States National Bureau of Standards, modernized Mendeleyevs periodic table. It got published in 1924. It was called the Periodic Chart of the Atoms. In the 1930s the heaviest elements were being put into the periodis table. The Alexander Arrangement of the Elements, a three-dimensional periodic chart designed and patented by Roy Alexander and introduced in 1994, retains the separate Lenthanide and Actinide series, but integrated them at the same time, made possible by using all three dimensions. The Periodic Table is an arrangement of the chemical elements. Its also an important reference for chemists and is the basis of chemical classification throughout the world. Bibliography Barlow, John Perry. The Elements Mar-Apr. 1995 Science Essays

Responding to Stress essays

Responding to Stress essays Suppose that you are in your car in the middle of a traffic jam heading home from school after a terrible day. You feel frustrated and groan as you think about the calculus midterm you have tomorrow, which you still have to study for. Suddenly, you have to hit the brakes. Your heart starts beating faster and you insult the driver whom nearly made you crash. Are these reactions normal? Indeed they are, since they are merely examples of stress. Many everyday circumstances, such as deadlines, tests, debts, and conflicts in personal relationships are stressful. Routine hassles at home, school, and work may create strain that affects mental and physical health and decreases the quality of life because tension accumulates. Stress is an everyday occurrence that renders emotional, physiological, and behavioral responses. When people are under stress, they usually react emotionally. Emotional responses are a natural and normal part of life, although most of the time stress tends to elicit unpleasant emotions rather than pleasurable ones. However, these unpleasant emotions serve an important purpose, since sometimes stress can make one cry and crying functions as an excellent therapy to get rid of pressure. Some common emotional responses to stress include irritation, frustration, and depression. For instance, because many people undergo mood swings and become irritated as a reaction to stress, they may end up hurting their relatives or friends. Even more, some people might become frustrated as they notice that they cannot achieve what they want at a particular moment. This frustration makes one feel hopeless and leads to depression. Depression is the most common emotional response to stress. People, not being able to adapt to change appropriately, may feel overwhelmed and often fail to recogn ize that they have a problem. When the situation comes to the point of depression, it is necessary to seek profe ...