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FCS Physics and Chemistry

The Atom
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Chemistry is the study of matter, which is anything that hass mass and volume.  You are made up of matter, as is your books, sneakers, etc.  Even the gases that make up our atmosphere are matter.  Chemistry is the branch of science that is concerned with the composition of matter and the changes that occur to it. 
This topic is an introduction to the foundations of matter, in terms of; basic classifications, how it was originally viewed and current thoughts, and the structure of the atom. 

The early studies of matter starts with the Greeks!  They viewed all matter to be composed of particles from four elemental substances
  • Earth
  • Wind
  • Fire
  • Water
This view was held until the 1600s when a man named Robert Boyle identified Gold and Silver as being elemental in themselves (the most basic)..and not made up of what the Greeks termed as an elemental substance
John Dalton built on Boyle's work and in the 1700s theorized that the basic unit of matter is called the ATOM and summarized his findings into four postulates
1. All elements are composed of indivisible atoms
2. All atoms of a given element are identical
3. Atoms of different elements are different and have different masses
4. Compounds are formed by the combination of atoms of different elements
That's great...atoms make up elements...elements make up compounds..but what is an ATOM composed of?
J.J Thomson discovers the on the tube!
Thomson proposed that the electrons might be imbedded in the atom...small negatively charged particles in a large positive sphere..he called this the Plum Pudding Model

Rutherford discovers the on the man!

Modern Atomic Theory


Neils Bohr proposed a model of the atom showing a dense nucleus with electrons found in surrounding orbits.  He later performed work on the hydrogen atom and comcluded that electrons can jump from a lower energy level (one closer to the nucleus) to a higher energy level by absorbing a specific amount of energy; this specific amout is equal to the energy difference between the two levels.  click on the Professor to find out more!

The Wave Mechanical Model advances the study of energy and atomic structure by modifying the atomic model.  Energy had been view as waves and matter as particles, however, in the late 1900s, energy and matter were viewed as acting as both..NOT as seperate entities, but with a dual nature.  In fact, energy is viewed to exists in discrete packets called quanta.   
This new model places the electrons not in specific orbits (as in Bohr's Model), but as packets with distinct amounts of energy moving in orbitals
An Orbital is described as a region in which an electron of a particular amount of energy might be found. 
The Wave Mechanical Model is our current view of Atomic Structure...

Atoms are composed of the following:
  • Protons: are positive, make up the bulk of the mass of the atom and are located in the center of the atom.
  • Neutrons: are neutral, just as massive as a proton and are also located in the center of the atom
  • Electrons: are negative, have a very timy mass and are located in orbitals surrounding the nucleus

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Forestville Central School
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Forestville, NY 14062