Download Atomic Structure and Stoichiometry Summary Sheet

Atomic
Structure
and
Stoichiometry
Summary
Sheet
2
“An
atom
is
the
smallest
particle
of
an
element
that
retains
the
chemical
properties
of
that
element.”
(Modern
Chemistry,
p.64,
2002)
I.
Atomic
Structure
A. Basic
structure
of
an
atom
1. Nucleus
–
center
of
the
atom
a. Proton
i. Positive
charge
ii. Determines
atomic
number
iii. Have
a
mass
unit
of
1
AMU
iv. Used
to
calculate
atomic
mass
b. Neutron
i. Neutral
charge
ii. Have
a
mass
unit
of
1
AMU
iii. Used
to
calculate
atomic
mass
iv. Number
of
neutrons
varies
in
isotopes
2. Electron
cloud—outer
portion
of
the
atom
a. Electron
i. Negative
charge
ii. Mass
not
significant
to
be
counted
in
the
mass
of
the
atom.
iii. Arrangement
determines
how
reactive
an
atom
is.
iv. Makes
up
most
of
the
volume
of
an
atom.
b. Orbital
i. A
three
dimensional
region
around
the
nucleus
where
a
particular
electron
might
be
found.
ii. Elements
in
the
same
GROUP
have
the
same
number
of
valence
electrons.
B. Atoms
are
electrically
neutral.
II.
Atomic
Theories
A. Law
of
Conservation
of
Mass
1. Mass
is
neither
destroyed
nor
created
during
ordinary
chemical
reactions
or
physical
change.
B. Law
of
Definite
Proportions
1. Chemical
compound
contains
the
same
elements
in
exactly
the
same
proportions
by
mass
regardless
of
the
size
of
the
sample
or
the
compound.
C. Law
of
Multiple
Proportions
1. If
two
or
more
different
compounds
are
composed
of
the
same
two
elements,
then
the
ratio
of
the
masses
of
the
second
element
combined
with
a
certain
mass
of
the
first
element
is
always
a
ratio
of
small
whole
numbers.
D. Dalton’s
Atomic
Theory
1. All
matter
is
composed
of
extremely
small
particles
called
atoms.
2. Atoms
of
a
given
element
are
identical
in
size,
mass
and
other
properties;
atoms
of
different
elements
differ
in
size,
mass
and
other
properties.
3. Atoms
cannot
be
subdivided,
created
or
destroyed.
4. Atoms
of
different
elements
combine
in
simple
whole
number
ratios
to
form
chemical
compounds.
5. In
chemical
reactions,
atoms
are
combined,
separated
or
rearranged.
E. Discovery
of
the
Electron
1. Cathode
Rays
Tubes
(Joseph
John
Thomson)
a. When
current
is
passed
through
a
cathode
ray
tube
the
surface
directly
opposite
the
cathode
glows.
b. Made
observations
using
cathode
ray
tubes
to
discover
the
negatively
charged
particle
called
the
electron
because
they
were
deflect
(repelled)
by
the
negatively
charged
side.
2. Millikan’s
experiments
a. Mass
of
the
electron
is
one
two‐thousandth
the
mass
of
the
simplest
type
of
hydrogen
atom.
b. Electron
mass
is
9.109
x
10‐31
kg
F. Discovery
of
the
nucleus
1. Ernest
Rutherford
a. The
volume
of
the
nucleus
is
very
small
compared
to
the
total
atom.
b. Gold
Foil
experiment
III.
IV.
V.
VI.
Counting
atoms
A. Atomic
number
=
number
of
protons
B. Isotopes
=
have
a
different
atomic
mass,
different
number
of
neutrons
than
the
“normal”
atom.
1. Are
used
to
calculate
the
atoms
average
atomic
mass.
C. Mass
Number
(Atomic
Mass)=Number
of
protons
+
neutrons
1. Average
atomic
mass=weighted
average
of
the
atomic
masses
of
the
naturally
occurring
isotopes
of
an
element.
D. Molar
Mass/Atomic
Mass/Formula
Weight
1. The
mass
of
one
mole
of
a
pure
substance
(g/mol)
Stoichiometry
A. Mole
(mol)=
Avagadro’s
number
of
anything,
the
amount
of
a
substance
that
contains
as
many
particles
as
there
are
atoms
in
exactly
12g
of
carbon.
B. Avagadro’s
number
=
6.022
x
1023
the
number
of
particles
in
exactly
ONE
mole
of
any
substance
1. Used
to
calculate
either
the
number
of
molecules
or
atoms
in
a
substance.
C. Gram/Mole
Conversions
D. Mole
ratio
=
a
conversion
factor
that
relates
the
amounts
in
moles
of
any
two
substances
involved
in
a
chemical
reaction.
Limiting
Reactions
A. Limiting
reactant
(reagent)=
the
reactant
that
runs
out
first
in
a
chemical
reaction
causing
the
reaction
to
stop.
B. Must
calculate
theoretical
yield
(mole
bridge)
to
determine
which
reactant
is
limiting.
C. Excess
reactant=
the
substance
that
is
not
used
up
completely
in
the
chemical
reaction.
Percent
Yield
A. The
ratio
of
the
actual
yield
in
an
experiment
compared
to
the
theoretical
yield
(mole
bridge)
%
yield
=
(actual
yield
/
theoretical
yield)
x
100
VII.
Percent
Error
A. How
much
the
actual
yield
deviates
from
the
theoretical
yield.
B. Used
to
determine
how
well
the
reaction
went.
%
error
=
{(theoretical
yield
–
actual
yield)
/
theoretical
yield}
x
100