Introduction
to Atoms
Exploring Inner
Space
Atom
The smallest particle
of an element…
makes up all matter.
Particle
Charge
Mass
Proton
+
+1 amu
Neutron
0
(neutral)
Electron
-
+1 amu
0 amu
amu= atomic mass unit
The most stable form
of an atom is
electrically neutral…
this means that the
number of protons &
electrons is equal.
Example=> Oxygen has 8
protons & 8 electrons
Nucleus: The center
of the atom
(contains protons
and neutrons).
Electron cloud:
electrons
orbit the
nucleus.
(contains
ONLY
electrons).
The
electrons
fill
energy
levels
within the
electron
cloud.
The number of
energy levels can
be determined by
the period
number on the
periodic table.
As a general
rule, there are
2 electrons in
the first energy
level, up to 8
electrons in the
second and 8 or
more in each
level after that.
Elements are atoms with the
same number of protons that
share the same physical and
chemical properties… the # of
protons determines the
element.
For example, hydrogen has only
1 proton in its nucleus,
Lithium has 3 protons, and
Oxygen has 8.
Atomic number = the
number of protons
in an atom
How many protons
does carbon have?
6
Almost
all of
the
mass of
an atom
is in the
nucleus.
electron
neutron
proton
Atomic mass =
# of protons +
# of neutrons
Carbon’s
atomic mass
is 12. Carbon
has how many
neutrons?
6
(atomic mass - # of protons = # of neutrons)
Every element is
represented by a
symbol… if it has one
letter, that letter is
capitalized
(C=carbon). If it has
two letters, the first
is capitalized and the
second is lower case.
(Na = sodium)