1) The Nuclear Atomic Model - N3.pdf - Our search to...


Our search to understand matter has been a
journey that dates back to Greek
philosophers over 2400 years ago

Democritus wondered if matter could be
divided into smaller and smaller pieces
forever, or was a limited number of times
matter could be divided?


Democritus theorized that matter could not
be divided smaller infinitely and that there
was the smallest piece of matter and it would
be invisible to the naked eye

He called this matter “ atomos ” which means
“not to be cut”


Democritus believed that atoms were small,
hard particles that were all made of the same
material but were different shapes and sizes

He also believed that atoms were infinite in
number, always moving and capable of
joining together


Democritus’ thoughts were largely forgotten
and ignored for 2000 years

At his time, Aristotle and Plato described
matter as being part of four elements:
▪
Earth
▪
Fire
▪
Air
▪
Water


Law of Definite Proportions: mass ratios of
elements in a compound are always the
same, therefore individual atoms of each
element are all alike

Law of Multiple Proportions: Atoms always
combine in whole number ratios (FeS or
FeS2, never FeS1.5) indicating they can’t be
broken apart


Limitation :
▪
Could not explain why atoms of
elements combine in the ratio they do

Despite this limitation, Dalton’s
work became the foundation of
modern chemistry