 Determines

the element
Number of protons CANNOT change for an element
 Common
charge notation is +1
 Mass (g) = 1.673 x 10-24
 Mass (amu)= 1.0073 = 1
 Common
charge notation is 0. No charge!
 Mass (g) 1.675 x 10-24 (same mass as proton)
 Mass (amu)= 1.0082 = 1
 Number of neutrons CAN change for an element

ISOTOPES
 Stabilizes
nucleus by nuclear force
 Common
Charge notation is -1
 Mass (g) of e- = 9.109 x 10-28
 Mass (amu)= .0006 = 0
 Number of electrons CAN change for an element

IONS
 Responsible
for chemical reactivity, forms bonds
Proton
Neutron
Electron
Nucleus
Nucleus
Outside of
nucleus
Common charge +
0
_
Mass, g
1.673x10-24
1.675 x 10-24
9.109 x 10-24
Mass, amu
1
1
0
Location
 Which
subatomic particle can NOT change for
an element and gives it’s identity?
 Which
subatomic particle stabilizes the
nucleus?
 Atomic
Number: The number of protons in
each atom of that element.

Unique to EACH element, never changes!!
 Neutral
atoms: proton #= electron #
 Example:
1.
2.
How many protons does Beryllium (Be)
have? How many electrons?
How many protons does Gold (Au) have?
 Isotopes:
Are atoms that have different
number of neutrons

So masses are different
Example of isotopes:
 Mass
Number: The total number of protons
and neutrons in the nucleus
 Element-
 What
Mass number
is the hyphen notation of lithium if the
mass number is 4?
Common isotopes of carbon
Carbon-12
Carbon-13
Carbon-14
How many protons do all the carbon isotopes
have?
How many neutrons do each of the carbon
isotopes have?
 Atoms
are Neutral because they have the
same number of electrons and protons

You will assume this unless indicated otherwise
 Ions
:are when the electron number and
proton number are different leading to a net
charge.
 What
charge would Aluminum have 13
protons and 10 electrons?
 NOTE:
YOU WILL ALWAYS ASSUME ATOMS
ARE NEUTRAL (protons = electrons) UNLESS
TOLD OTHERWISE
Atomic
#= Proton #= Electron #
(because we assume atoms are neutral)
Mass
#= Atomic # + Neutron #
Number of protons= Atomic number
 Number of electrons = Number of protons (in a
neutral atom)
 Number of neutrons = Mass number– Atomic
number

Symbol
Atomic
#
Na
11
15
Mass #
31
# of
protons
# of
electrons
# of
neutrons
 Average
atomic mass is the weighted
average of the atomic masses of the
naturally occurring isotopes of an element

This number appears below the element
symbol on the periodic table.