CHEMISTRY DIAGRAMS
Bohr Rutherford and
Lewis Dot Diagrams
RECALL THE ATOM
• ATOMIC NUMBER:
denotes the number of
protons and electrons in
an atom
• ATOMIC MASS:
denotes the number of
protons plus neutrons in
the nucleus of an atom
HOW DO YOU FIND NUMBER OF
NEUTRONS
• # of Neutrons = ATOMIC MASS – ATOMIC NUMBER
• EXAMPLE: How many neutrons are there in a
Silicon atom?
• SOLUTION:
28
Atomic Mass
--
14
=
14
--
Atomic
Number
=
Number of
Neutrons
BOHR RUTHERFORD DIAGRAMS
• Used to show the atomic structure of an atom,
isotope or ion.
BOHR RUTHERFORD DIAGRAMS
• RULES for drawing Bohr Rutherford diagrams:
1. Place the number of protons and neutrons in the
nucleus of the atom
2. Place TWO electrons in the first shell. This shell
takes a MAX of two electrons.
3. Place a MAX of eight electrons in all other shells.
4. OCTET RULE: No shell can have more that
EIGHT electrons. If you have extra electrons, add
another shell.
PRACTICE
• Draw a Bohr Rutherford diagram
for:
a. Boron
b. Fluorine
c. Argon
LEWIS DOT DIAGRAMS
• Used to show the
number of
electrons in the
outer shell of an
atom
LEWIS DOT DIAGRAMS
• RULES for drawing Lewis Dot Diagrams
1. Write the chemical symbol for the element.
2. Determine the number of electrons in the outer shell
of that element.
3. Add electrons starting at the top of the chemical
symbol and working CLOCKWISE around the
symbol.
4. You MUST add ONE electron to each side of the
symbol BEFORE you start pairing electrons.
PRACTICE
• Draw a Lewis Dot Diagram for the
following elements:
a.Boron
b.Fluorine
c.Argon