SECTION 1: STRUCTURE
OF THE ATOM
Chapter 17: Properties of Atoms
LEARNING GOALS
Identify
the names and symbols of
common elements.
Identify
quarks as subatomic
particles of matter.
Describe
the electron cloud model of
the atom.
Explain
how electrons are arranged
in an atom.
WARM-UP:
Agree or
Disagree
SCIENTIFIC SHORTHAND
Each
element can be symbolized with
a chemical symbol.
 A short or abbreviated way to write the
name of an element.
 Consist of one capital letter plus one or
two small letters.
SCIENTIFIC SHORTHAND
Some
elements use the first letter or
letters of their name to symbolize the
element:
 Aluminum (Al)
 Calcium (Ca)
 Carbon (C)
 Nitrogen (N)
SCIENTIFIC SHORTHAND
The
symbols of other elements are
derived from Latin:
 Sodium (Na)
 Silver (Ag)
 Gold (Au)
 Potassium (K)
ATOMIC COMPONENTS
An
element is
composed of one
type of atom.
 Atom: the smallest
piece of matter
that still retains the
properties of that
element.
ATOMIC COMPONENTS
Atoms
are composed of particles
called protons, neutrons, and
electrons.
ATOMIC COMPONENTS
Protons
and neutrons are found in a
small, positively charged center
called the nucleus.
proton
neutron
ATOMIC COMPONENTS
Protons
are particles with an electrical
charge of 1+
 They are made up of even smaller particles
called quarks.
 Different elements have different numbers
of protons
ATOMIC COMPONENTS
Neutrons
are particles that do not have
an electrical charge.
 They are also made up of even smaller
particles called quarks.
 The number of neutrons in a single element
may vary
ATOMIC COMPONENTS
Electrons
are particles
with a charge of 1 Electrons are 1/1836 the
size of a proton and can
be found somewhere in
the electron cloud.
 The number of electrons
in a single element may
vary
ATOMIC MODELS
Atoms
are incredibly small!
 It would take 24,400 atoms stacked one
on top of another to equal the
thickness of a sheet of aluminum foil.
We
need models in order to visualize
and understand the atom.
ATOMIC MODELS
400
B.C.
 Democritus proposed the idea that
substances were made up of tiny,
indestructible particles called atoms.
 Aristotle claimed that matter was
uniform throughout and could be made
of earth, water, air, or fire.
Aristotle’s theory was accepted for the next
2,000 years!

ATOMIC MODELS
1805:
 John Dalton offered proof that atoms exist
 Created an early model of the atom that
showed a simple sphere
ATOMIC MODELS
1926:
 The electron cloud model was developed
and is still used today
 Electron cloud: the area around the nucleus
of an atom where its electrons are likely to
be found.
ATOMIC MODELS
 The electron cloud is 100,000 times larger
than the diameter of the nucleus.
 Because electrons are so small and move so
quickly, it is impossible to describe their
exact locations.
CHECK-IN:
Identify
the names, charges, and
locations of three kinds of particles
that make up an atom.