Download 794128Introduction_to_Atoms

Introduction to Atoms
History of the Atom

Democritus


Proposed matter made
of atoms (meaning
“indivisible”)
Dalton



All substances made
of atoms.
Atoms of same
element are alike.
Atoms join with other
atoms.

Thompson



Cathode-Ray
Experiment.
Found negative
particles called
electrons.
Plum pudding model


Positive material
Electrons throughout

Rutherford

Gold foil experiment

New atomic model

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
Nucleus
Empty space
Electrons orbit the
nucleus.

Bohr


Electrons travel in
paths or levels around
the nucleus.
Modern Theory


Electrons are found in
regions, not exact
paths.
Electron clouds.
Structure of an Atom

Smallest part of an
element.

Made of protons,
neutrons, and
electrons.

Want a total charge of
zero.

Electrons




Negative charge
No mass
Found outside of nucleus
Nucleus

Protons

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Positive charge
Mass of 1 amu
Neutrons


No charge
Mass of 1 amu
Vocabulary

Ion


Atomic number


Same protons, different
neutrons.
Mass number


Number of protons.
Isotope


Atom with a charge.
Sum of protons and
neutrons.
Atomic mass

Average of all natural
isotopes.
Periodic Table of Elements


Mendeleev developed
the table.
Classes of Elements

Metals


Nonmetals

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Conductors, shiny,
ductile, malleable.
Not like the metals.
Metalloids

Properties of both.
The Element Key

Atomic Number

Chemical Symbol
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Element Name

Atomic Mass

Class & State of Matter