1. Unit 8: Ch. 4 & 5 ATOMIC STRUCTURE
*An atom is the smallest particle of an element that retains its identity in a chemical reaction.
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2. DEMOCRITUS’S ATOMIC PHILOSOPHY
*He believed that atoms were indivisible and indestructible.
His ideas agreed with later scientific theory but they did not explain chemical behavior.
*His ideas were faulty because they lacked experimental evidence.
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JOHN DALTON
John Dalton was an English chemist and schoolteacher.
His ideas came more than
2000 years after Democritus.
***He used experimentation
to change Democritus’s
theory into a legitimate
scientific theory.
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6. DALTON’S ATOMIC THEORY
*All elements are composed of tiny indivisible particles called atoms.
*Atoms of the same element are identical and atoms of different elements are different.
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7. DALTON’S ATOMIC THEORY continued
*Atoms of different elements can physically mix together or they can chemically combine to form compounds.
*Chemical reactions occur when atoms are separated, joined or rearranged.
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THE SIZE OF ATOMS
*Individual atoms are very small.
The radii of atoms are between m & m
*Despite their small size, individual atoms can be seen with scanning tunneling microscopes.
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element At # p n mass #
Page 3 C H H N Cs
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symbol At # p n e At mass #
Page 4 C W Cr
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element p n e At mass At #
Page 5
lithium
carbon
chlorine
silver
lead
calcium
tantalum
radium
samarium
uranium
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