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Unit 3 Lesson 1 (John Dalton (theory based on evidence, stated all matter…
Unit 3 Lesson 1
John Dalton
theory based on evidence
stated all matter made of atoms
thought all atoms cannot be created, divided, or destroyed
also stated all atoms of certain element are identical
also thought atoms join with other atoms to make new substances
every substance made up of atoms combined in a certain way
Niels Bohr
made observations leading to new theory of how electrons in atoms behaved
Agreed atom has positive nucleus surrounded by electrons
in his model electrons move around the nucleus in certain path
model helped scientists predict chemical properties of elements
scientists have since made observations that couldn't be explained by his model
model of atoms been revised to explain these observations
Democritus
Greek around 400 BCE
thought you would end up with a a particle that couldn't be cut
Called this particle "atomos"
atomos- not able to divide
J.J. Thomson
experiments provided evidence that atoms are made up of even smaller particles
Found particles within the atom that have negative charge
negatively charges particles- electrons
thought atom was a positive sphere with electrons mixed through
Ernest Rutherford
1909 did an experiment to study parts of an atom
suggested atoms have a nucleus
nucleus- small, dense center w/ positive charge and surrounded by moving electrons
Later found nucleus made up of smaller particles
called positively charged particles in nucleus protons
Aristotle
He disagreed with Democtritus
thought no such particle could make up all substances
neither did experiments to further their beliefs