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Atomos: that which cannot be cut.
B. Definition of Atom: the smallest unit of matter which still retains the
identity and properties of that matter. -
Refuted Democritus
Believed in four elements: Earth, Air, Fire, and Water.
Aristotle’s refutation of Democritus’ Atomic Theory led to nearly
2000 years of bogus “science” Among the most prominent: -
332 BC Alexander the Great had conquered Egypt
Greek philosophers became interested in the Egyptian religion. Greek
views of how matter is made up of the four elements of nature were
merged with Egyptian religion.
The result was Khemia, the Greek word for Egypt.
The word Alchemy came from the word Khemia, which means Egypt.
@600 A.D. Arabs occupied Egypt and further developed the science,
spread it to the West (Spain) in 700s. -
from the Ancient Greek phlogistón "burning up"
first stated in 1667 by Johann Joachim Becher
postulated the existence of a fire-like element called "phlogiston",
which was contained within combustible bodies and released
during combustion.
A substance that burned did so because it contained Phlogiston.
Carbon Dioxide, no longer capable of burning was called
“dephlogisticated air” -
Father of Modern Chemistry because he relied on quantitative
observation to develop conclusions.
Dispelled the Phlogiston Theory by proving that Oxygen causes
combustion.
Discovered the Law of Conservation of Mass: By proving that the
mass of a metal oxide = the mass of the metal plus oxygen when
the metal oxide decomposes.
Matter can change form, but cannot be created nor destroyed
in a chemical reaction.
Beheaded during French Revolution -
Discovered that electrical charges come in 2 varieties – positive and
negative. Like charges repel, opposite charges attract. -
The Law of Definite Proportions, sometimes called The Law of
Constant Composition, states that a chemical compound always
contains exactly the same proportion of elements by mass. -
Dalton’s Atomic Theory of Matter:
A. Matter is made up of atoms that are indivisible and indestructible.
B. All atoms of an element are identical. (Known now to be untrue!)
C. Atoms of different elements have different weights and different
chemical properties.
D. Atoms of different elements combine in simple whole numbers to
form compounds.
E. Atoms cannot be created or destroyed. When a compound
decomposes, the atoms are recovered unchanged.3 -
He discovered the element thallium and worked on his cathode-ray studies
-
He continued experimenting on the CRT.
JJ Thomson used charged plates to deflect the cathode ray. Found the ray deflected away from the negative plate, and toward the positive. -
He classified radiation
-
He discovered radioactivity in Uranium ore.
-
They discovered and isolated polonium and radium from uranium ores.
-
He calculated the mass and charge of an electron.
-
He provided that neutrons had no charge.
