MODELING ATOMS
AIM: HOW CAN WE MODEL ATOMS?
Chapter 2: section 1 (Continued)
WHAT IS A MODEL?
A model is an image which can show a smaller
version of a larger object or show a larger version
of a smaller object.
 It allows you to see the entire image in detail.
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THE HISTORY OF THE ATOMIC MODEL

Democritus
He proposed that matter is composed of small
particles.
 He called these small particles atoms.
 He also proposed different types of matter were
composed of different types of atoms.
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John Dalton


He expanded on Democritus' ideas.
He theorized that all atoms of an element
contain the same type of atom.
REVIEW: WHAT ARE THE THREE PARTS OF
AN ATOM AND THE CHARGES?

1)
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2)
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3)
THE HISTORY OF THE ATOMIC MODEL

Niels Bohr
He proposed that an atom’s electrons travel in orbit
like paths around the nucleus.
 He also proposed that electrons around the atom
have energy that depends on their distance from the
nucleus.

Electrons that are in paths closer to the nucleus have less
energy.
 Electrons that are in paths further to the nucleus have
more energy.

THE HISTORY OF THE ATOMIC MODEL:
THE CURRENT ATOMIC MODEL

Research has now showed electrons can be
grouped into energy levels, each holding only a
specific number of electrons.
Secondly, electrons do not follow an orbit like
path. They may exist anywhere within the
electron cloud.
 Evidence suggests they are abundant near the
nucleus.
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