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Atomic Structure
Chapter 4
Lesson 1
Early Models of the Atom
First:
A definition:
An atom is the smallest particle of an element that
retains its identity in a chemical reaction. (p101)
Early Models of the Atom
Democritis (before 370 BC):
Atoms are indivisible
Atoms are indestructible
Not possible to do experimental research
on atoms due to lacking technology.
Early Models of the Atom
Dalton’s Atomic Theory (Between 1766-1844)
All elements are composed of tiny indivisible
particles called atoms.
Atoms of the same element are identical. The
atoms of any one element are different from
those of any other element.
Early Models of the Atom
Dalton’s Atomic Theory (Between 1766-1844)
Atoms of different elements can physically mix
together or can chemically combine in simple
whole-number ratios to form compounds.
Chemical reactions when atoms are separated,
joined, or rearranged. Atoms of one element
are never changed into another element as a
result of a chemical reaction.
Early Models of the Atom
Even though some parts of Dalton’s theory
have been disproven, its pretty good
knowing that he died more than 30 years
before Edison invented electric lightbulbs.
Early Models of the Atom
A question:
What happens to atoms in a chemical reaction
according to Dalton’s Theory?
Sizing up the Atom
A pure copper penny contains about
2.4 x 1022 atoms (the human population in
the universe is 6 x 109 people
A line of 6x109 copper atoms would be
only 6cm (2 3/8 inches) long.