Warm Up
• What did Neils Bohr discover
about atoms?
• Why was this discovery so
important?
Atomic Notation
• Sometimes, elements are represented in atomic notation.
• This is usually true when they are not seen on the periodic
table
• The top number is the
Mass number and the
Bottom number is the
Atomic number.
YOU CAN TELL THE
DIFFERENCE BECAUSE
THERE IS NO BOX AROUND
THE ELEMENT SYMBOL
Practice
What is the atomic #?
What is the atomic mass?
Bohr-Rutherford Diagrams
Drawing Bohr-Rutherford Diagrams
• Electrons are found in atoms in ENERGY
LEVELS
– Each ring is called a SHELL
• The outermost electrons
are called VALENCE electrons
• In the periodic table,
elements can be found
arranged by its number
of valence electrons
Shells
The first shell can only hold 2 electrons.
The second, third, and fourth shells can hold 8
electrons.
Fill in the electrons starting at the center and
working your way out.
Watch a demonstration…
http://youtu.be/sKAzHE7A7rQ
As you watch the second demonstration, draw
along with the presenter. You will be drawing a
diagram for phosphorous.
http://youtu.be/M4dfgCfLNE8
Get a blank sheet of paper
• Your assignment is to draw Bohr Rutherford
diagrams for the first 20 elements of the
periodic table.
• If you do not finish, they are due for
homework on Monday!
• There is a Periodic table on the back inside
cover of your book and one in your agenda.
EXAMPLE
Name of
element
40
Calcium
Ca
20
11
B
5
20
Ne
10
Atomic
number
# of
protons
# of
electrons
# of
neutrons
Atomic
mass
number