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Historical development of atomic theory
Essay on the development of the atomic theory
Essay on the development of the atomic theory
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Democritus was a Greek philosopher who lived between 470-380 B.C. He developed the concept of the 'atom', which in Greek mean indivisible. Democritus have made many very important discoveries in his lifetime but the greatest was about the atom. Democritus believed that if you tried to cut matter into the smallest pieces possible, you would eventually get a very small particle that is indestructible and could not be cut. So Democritus did his first experiment by getting seashell and break it in half. He then took that half and broke it in half over and over and over again, until he was finally left with a fine powder. He then took the smallest piece from the powder and tried to break it again but he could not break it anymore. And that’s also …show more content…
His first experiment was to build a cathode ray tube with a metal cylinder on the end. This cylinder had two slits in it, leading to electrometers, which could measure small electric charges. In the late 19 Thomson began to experiment it with cathode ray tubes. Cathode ray tubes are sealed glass tubes from which most of the air has been evacuated. A high voltage is applied across two electrodes at one end of the tube, which causes a beam of particles to flow from the cathode, the negatively charged electrode to the anode of the positively-charged electrode. The tubes are called cathode ray tubes because the particle beam or cathode ray originates at the cathode. The ray can be detected by painting a material known as phosphors onto the far end of the tube beyond the anode. The phosphors spark, or emit light, when impacted by the cathode ray. This experiment led him to fins that by applying a magnetic field across the tube, there will not be activity recorded by the electrometers and so the charge will have to bend away by the magnet. This proved that the negative charge and the ray were inseparable and intertwined. …show more content…
A closed chamber with transparent sides is fitted with two parallel metal plates, which acquire a positive or negative charge when an electric current is applied. At the start of the experiment, an atomizer sprays a fine mist of oil droplets into the upper portion of the chamber. Under the influence of gravity and air resistance, some of the oil droplets fall through a small hole cut in the top metal plate. When the space between the metal plates is ionized by radiation, electrons from the air attach themselves to the falling oil droplets, causing them to acquire a negative charge. A light source, set at right angles to a viewing microscope, illuminates the oil droplets and makes them appear as bright stars while they fall. The mass of a single charged droplet can be calculated by observing how fast it falls. By adjusting the potential difference, or voltage, between the metal plates, the speed of the droplet’s motion can be increased or decreased; when the amount of upward electric force equals the known downward gravitational force, the charged droplet remains stationary. The amount of voltage needed to suspend a droplet is used along with its mass to determine the overall electric charge on the droplet. Through repeated application of this method, the values of the electric charge on individual oil drops are always whole-number multiples of a lowest value that value being the elementary electric charge itself. From the time
... middle of paper ... ... We can trace the origins of modern scientific trends back to Greek primal establishment. From the simplistic Socratic approach of ‘Who am I?’
...the mass spectrometer. This is called an electron impact source. Gases and volatile liquid samples are allowed to leak into the ion source from a reservoir. Non-volatile solids and liquids may be introduced directly. Cations formed by the electron bombardment (red dots) are pushed away by a charged repeller plate (anions are attracted to it), and accelerated toward other electrodes, having slits through which the ions pass as a beam. Some of these ions fragment into smaller cations and neutral fragments. A perpendicular magnetic field deflects the ion beam in an arc whose radius is inversely proportional to the mass of each ion. Lighter ions are deflected more than heavier ions. By varying the strength of the magnetic field, ions of different mass can be focused progressively on a detector fixed at the end of a curved tube. Because the mass of each individual ion
An ion is a “electrically charged atom or groups of atoms”. (works, 2009)Referring to positively and negatively charged atoms that are used to form an ion. A document discusses how in order for an atom to become an negative ion it has to receive/gain electrons. However for a atom to become a positive ion it has to lose electrons. Another name for a negative ion is anion and another name for a positive ion is cation. This is also known as the Ionization process. Ionization in general can take place in an liquid, solid, and/or gases. Ions are also known to form when a dissociation is occurred. When this particular process begins to occur oppositely charged ions begin to dissolve for example in water or another form of solvent. These are known as electrolytes When a These terms are important to know because the experiment deals with an ion space system. Including but not limiting to acids, bases, and salts. These are often a good conductor for electricity which is why they are typically used for these space engines. (works, 2009). It is important to understand the ion and how it is formed and why it reacts because it is used in our experiment. Which would help to better understand what everything is talking about. Especially since the ...
X-rays were discovered by accident in 1895 by the German physicist Wilhelm Conrad Roentgen. Roentgen was already an accomplished scientist with forty-eight published papers. He had a reputation among the scientific community as a dedicated scientist with precise experimental methods. Roentgen had been conducting experiments at the University of Wurzburg on the effect of cathode-rays on the luminescence of certain chemicals. Roentgen had placed a cathode-ray tube, which is a partially evacuated glass tube with metal electrodes at each end, in a black cardboard box in his darkened laboratory. He sent electricity through the cathodre-ray tube and noticed something strange his laboratory. He saw a flash of light from a sheet of paper coated with barium platinocyanide that he had unknowingly left on a table at the other end of the lab. Roentgen knew that cathodre-rays could not penetrate the black box and that they only travel short distances. So he deduced that another form of radiation emitted from the cathode tube was causinq the luminescence. Roentgen called this new unknown radiation X-rays. X being the mathematical symbol for a unknown.
(CITE) J. J. Thompson discovered the electron in 1897 while showing what cathode rays were composed of. (CITE) The first time that the electron was used for a unit of negative electricity was in the late 19th century by the English physicist G. J. Stoney.
How can you tell if an object is charged? How can you tell if an object is positively or negatively charged? How can you tell if an electroscope is positively or negatively charged?
One of the first and greatest Greek philosophers was a man named Democritus. He is not as well-known as other great philosophers like Socrates, Plato, or Aristotle but he contributed greatly on the development of philosophy up until today. He, along with all pre-socratic philosophers, was a natural or physical philosopher. He is sometimes referred to as the father of modern sciences after his major discoveries and works. He was born in the city of Abdera, Greece, although some reports called him a Milesian, on c. 460 BCE and died at the age of about 90 years on c. 370 BCE. He was born to a wealthy family and enjoyed traveling. He was known as the laughing philosopher because of he emphasized the importance of the value of cheerfulness. Democritus is said to have written more than 70 books but none of them survived. Most of his works were unreliable because they, along with the works of most ancient Greek philosophers, were only in secondhand reports. Most of his works were told secondhand by another great philosopher named Aristotle because he considered Democritus as his biggest rival in the natural sciences. He seems to have taken over the works of his mentor, Leucippus. Both of them were very accomplished. His knowledge was vast for he worked on different fields such as cosmology, music, mathematics, ethics and physics (Stanford Encyclopedia of Philosophy, 2004).
The concept of the atom originated in Greek philosophy around six hundred B.C. with the question: ¡§What is the world made of ?¡¨ (Sachs, 9). Thales first suggested that ¡§water [is] the basic building block of the world¡¨, and air, sand, and stone could be different forms of one fundamental substance (web page). Yet, Anoimenes believed ¡§mist or air was the cornerstone of matter¡¨ (Clagett, 49). These ancient thinkers made simple and direct assertions about matter. Later, the idea of the atom was conceived and developed by Leucippus and Democritus in the fifth century B.C. and concluded that there must be ¡§parts which are partless¡¨ such as sand, stone, water, or even a ¡¥void¡¦ which have the continuous and coherent appearance of a pure object though are not ¡¥true¡¦ structures (Young, 18).
Scientists established by the early 1900s that atoms contain electrons and their electrically neutral. They also knew that to maintain an electrically neutral, an atom must contain an equal amount of positive and negative charges. The knowledge that was proposed by many scientists led to Thomson proposing the so-called “plum pudding model”. The plum pudding model included a positive sphere of matter, where negatively charged electrons embed the sphere looking like raisins in a cake. This theory was the accepted theory for a number of years until a scientist named Ernest Rutherford decided to probe the structure of an atom using α particle.
John Dalton is one man that made a great impact in the field of chemistry. Without his contribution to the “Atomic Theory," our modern technology and science would not be the same. Without John Dalton, we will never know if G.J Stoney was able to discover the “Electron” or Wilhm Roentgen discovers the “X-Ray," or Marie Slodwka Curie discovers the “Radioactivity," Albert Einstein discovers the “E=MC^2," or the completion of the “Periodic Table” by Dmitri Mendeleev (Buescher,
How to test for this: a Metal plate is attached to a galvanometer with two wires, if a light with the right frequency and wavelength is shone upon it, a current will be registered with the galvanometer. (A Galvanometer measures the electric current and the flow of it.) The readings might show that electrons have been ejected. The ejected electrons flow through wires to the galvanometer and that causes a reading.
There are many different experiments which can give varying intelligence about the makeup of matter, in different ways and with different conclusions. In this instance I will be looking at the discovery of the electron, how our understanding of it has changed over the years, and measure how it has contributed to where we are today.
In 1831, using his "induction ring", Faraday made one of his greatest discoveries - electromagnetic induction: the "induction" or generation of electricity in a wire by means of the electromagnetic effect of a current in another wire. The induction ring was the first electric transformer. In a second series of experiments in September he discovered magneto-electric induction: the production of a steady electric current. To do this, Faraday attached two wires through a sliding contact to a copper disc. By rotating the disc between the poles of a horseshoe magnet he obtained a continuous direct current. This was the first generator. From his experiments came devices that led to the modern electric motor, generator and transformer.
The gold-foil sheet experiment involved the firing of radioactive alpha particles to a thin gold foil sheet, and detecting them using screens to see the direction of their deflection. Most of the particles passed straight through the foil, except one. This reflection, led to the creation of his theory which stated that most of the atom was empty space, and the discovery of a very densely packed bundle of matter with positive electric charge. (Editors of Encyclopedia Britannica, 2014.)
1876: Boston civil servant George Carey was thinking about complete television systems and in 1877 he put forward drawings for what he called a "selenium camera" that would allow people to "see by electricity." Eugen Goldstein coins the term "cathode rays" to describe the light emitted when an electric current was forced through a vacuum tube.