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Gathering Atomic Information
ALMOST ALL OF THE INFORMATION YOU
NEED TO KNOW ABOUT A PARTICULAR
ELEMENT CAN BE FOUND BY LOOKING AT
THE PERIODIC TABLE. THE PERIODIC
TABLE WILL TYPICALLY HAVE ONE OF THE
FOLLOWING FORMATS:
If this stadium were the size of an atom’s electron cloud, the
nucleus would be the size of a marble setting on the 50 yard
line. Electrons occupy the VOLUME, protons and neutrons
constitute the MASS of an atom.
Subatomic Particles
 Protons and electrons are the only particles
that have a charge.
 Protons and neutrons have essentially the
same mass.
 The mass of an electron is so small (2000
time smaller than the proton), we ignore it.
0.0005486 is the way to write this number!
3
What do all atoms of the same element have in
common?
***Atoms of the same element always contain
the same number of protons!***
What is the name of the two numbers on an
element’s square of the periodic table?
Carbon
12.011
C
6
 Atomic Number:



Smallest of the two numbers
Always a whole number
Indicates number of protons
 Average Mass


Average number of protons (p+) and neutrons
Usually a decimal
 Mass Number


# of protons and neutrons added together
round the average atomic weight to the nearest
whole number to find the most common
combination of p+ and n (isotope)
6
C
Carbon
12.011
What information can be obtained from the two
numbers on a square of the periodic table?
Subatomic
Particle
&
symbol
Charge
Mass
(amu)
Location
(region)
How to
find
number in
an atom
Founder
and Date
Proton
(p+)
Positive
(+)
1
Nucleus
Same as
atomic
number
E.
Rutherford
1914
Neutron
(n) or (0)
Neutral
1
Nucleus
Mass #
-Atomic #
# Neutrons
J Chadwick
1932
Electron
(e-)
Negative
(-)
0
Electron
cloud
Same as
JJ Thomson
atomic
1897
number in a
neutral
atom
How are the particles related?
Atoms
Electron Cloud
Nucleus
Region
Subatomic
Particle
Charge
Charge Balance
Neutron
0
Proton
+
electron
-
Isotope
ATOMS OF THE SAME ELEMENT
THAT HAVE DIFFERENT
NUMBER OF NEUTRONS
Models of Carbon Isotopes
Carbon-12
6p+
6n
Carbon-13
6p+
7n
Carbon-14
6p+
8n
 How are isotopes of the same element identified?
 Isotopes are identified by the name of the element and by the
atom’s mass number (written like Li-6 or Li-7)
 It’s called ISOTOPE NOTATION
Lithium Isotope Examples
Isotope
Name
Symbol
# protons
# neutrons
# electrons
Lithium-6
Li-6
3
3
3
Lithium-7
Li-7
3
4
3
Chlorine-35
Cl-35
17
18
17
Chlorine-37
Cl-37
17
20
17
How to find Mass Number
 Number of protons AND neutrons (added together) of a
specific isotope of an element.
 Mass Number = #p + #n
 Found one of two ways (prioritized)

Given to you after the element symbol (isotope notation)
C-14 or Na-23
 100% accuracy


Most common isotope method (mci). Round the average atomic
mass value from the periodic table to the nearest whole number
Carbon’s Atomic mass is 12.011 = round to 12
 Manganese’s Atomic mass is 54.95 = round to 55
 50% accuracy
