 Atoms
 Make
up all matter
 Made up of smaller
particles called:
protons
neutrons
electrons
These were not
known until 100
years ago, very
short amount of
time in perspective
 Parts
of an atom
 Nucleus:
center of
an atom—
extremely small
 Plural--nuclei
 Houses the protons
and neutrons
 Protons
 Positive
charge
 labeled with a +
sign
 p+ = proton
 Neutrons
 No
charge
 Neutral
 Electron
 Negative
charge
 e Orbit
in the space
outside the
nucleus
 Rapidly move
around the outside
of the nucleus
 Electron
clouds
 Travel
in a sphereshaped region
 The electrons may
be anywhere
inside the cloud
 Electrons with
higher energy
move farther away
from the nucleus
within the sphere
 Electron
Cloud
 Most
of the volume
of an atom is
made up of the
electron cloud
 Enormous
compared to the
nucleus
 VERY SMALL (mass)
 2,000 electrons = 1
proton
 Protons
and
Neutrons
 Make
up the
majority of an
atoms mass
 Atoms
 Too
small to be
measured in
everyday units of
mass
 Measured in atomic
mass units (amu)
 Measurement
 Proton
= 1amu
 Neutron = 1amu
 Electron = 1/2000
of an amu
 Element
 I.D.
by the # of
protons in the
nucleus of its
atoms
 Every element is
different.
 Atoms are
different in every
single element
 Atomic
number
 Isotopes

the number of
protons in an atom’s
nucleus
 Elements
with the
same protons but
different neutrons
 All atoms of the
element have the
same proton
 The NEUTRONS can
vary
 Mass
Number
 Identifies
different
isotopes
 Sum of protons and
neutrons
 Written as; carbon12
carbon-14, carbon-13
 Even with different
isotopes they react
the same chemically
 Models
 Scientists
create
models to study
atoms
 Any diagram,
mental picture,
mathematical
statement, or an
object that helps
explain details and
ideas about the
natural world