Atomic Theory

Topics: Atom, Electron, Cathode ray Pages: 4 (1235 words) Published: January 2, 2013
1. a) Democritus reasoned that if matter could be infinitely divided, it was also subject to complete disintegration from which it can never be put back together. However, matter can be reintegrated.

b) In Greek, the prefix "a" means "not" and the word "tomos" means cut. Our word atom therefore comes from atomos, a Greek word meaning uncuttable. All matter is composed of atoms, which are bits of matter too small to be seen. These atoms CANNOT be further split into smaller portions.

2. At this point, the atomists entered into what their predecessors had postulated to be the origin of matter, namely water (Thales), air (Anaximenses), fire (Heraclitus) and earth (Empedocles). They said, quite accurately as we know today, that these four elements are not primordial substances, but are composed of atoms like everything else.

All matter consists of tiny particles called atoms
-Atoms are indestructible
-All atoms of an element are identical
-Atoms of different elements have different masses
-When elements react, their atoms combine in simple, whole number ratios Some of the details off Dalton’s original theory are now known to be incorrect. But the core concepts of the theory (that chemical reactions can be explained by the union and separation of atoms, and that these atoms have characteristic properties) are foundations of modern physical science.

4. Dalton and a few Greek philosophers proposed that matter is discrete. Beyond a certain point, a substance cannot be cut into smaller pieces that retain the properties of the whole. They called the smallest possible piece an “atom”.

5. Sir William Crookes gained more knowledge about the mysterious green glow when he created a bent Geissler tube in 1875. He noticed that the glow was the most intense opposite the negative electrode, also called the cathode. Crookes reasoned that rays traveled from the cathode and then hit the end of the tube. Because of this, Crookes named these rays...
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