Chemical Models of
Elements
Bundle 6: Periodic Table &
Models Section
Drawing Bohr Models
Bohr Models
1.
2.
3.
Bohr models are used to predict
reactivity in elements.
Reactivity refers to how likely an
element is to form a compound with
another element.
When looking at Bohr models, we look at
its valence electrons (the electrons on
the last energy level) to determine
reactivity.
Drawing Bohr Models
1.
2.
3.
4.
5.
Draw the nucleus.
Write the number of neutrons and the number
of protons in the nucleus.
Draw the first energy level.
Draw the electrons in the energy levels
according to the rules below. Make sure you
draw the electrons in pairs.
Keep track of how many electrons are put in
each level and the number of electrons left to
use.
Rules for Energy Levels
1.
2.
3.
4.
Level 1 (closest to the nucleus) can hold
a maximum of 2e.
Level 2 can hold a max of 8e.
Level 3 can hold a max of 18e.
Level 4 can hold a max of 32e.
You must fill one level before going on to
draw the next level!
How to determine the # of
Neutrons
 The
Atomic Mass of an element from the PT
is an AVERAGE Mass of all of the elements
isotopes. (Remember Hydrogen)
 For a NEUTRAL atom, round the Atomic
Mass to the nearest whole number. This will
be the ESTIMATED number of neutrons in
the nucleus of the atom.
 To know the EXACT number of neutrons, you
must be given the EXACT Atomic Mass.
Guided Practice
In order to draw Bohr models of these elements, you
must first determine the number of protons, neutrons,
and electrons. Once you have found this information,
follow the directions to draw your model.
6
C
Carbon
12.011
6
6
6
Protons: _____
Neutrons: _____
Electrons: ______
2
How many energy shells will this have? ____
4
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
16
S
Sulfur
32.066
16
16
16
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
6
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
3
Li
Lithium
6.941
3
4
3
Protons: _____
Neutrons: _____
Electrons: ______
2
How many energy shells will this have? ____
1
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
10
Ne
Neon
20.180
10
10
10
Protons: _____ Neutrons: _____ Electrons: ______
2
How many energy shells will this have? ____
8
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
15
P
Phosphorus
30.974
15
16
15
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
5
How many valence (outer) electrons does this element have? ____
Bohr Model:
Guided Practice
11
Na
Sodium
22.990
11
12
11
Protons: _____
Neutrons: _____
Electrons: ______
3
How many energy shells will this have? ____
1
How many valence (outer) electrons does this element have? ____
Bohr Model:
Lewis Dot Structures
 Here’s
a short video on how to draw
Lewis Dot Structures.
https://www.youtube.com/watch?v=HCOI4
-AYA1U
Lewis Dot Structures
 Lewis

Dot Structure
Illustrates the number of VALENCE Electrons
• Valence electrons = Number of electrons in the
outermost energy shell
• Placed around the symbol of the element

Helps us determine how compounds are formed
/ how elements bond
 Electrons
should be drawn in pairs around
the element.
 A Lone Electron is called a BONDING SITE
which we will cover more in the Bonding Unit.
Drawing Lewis Dot Structure
1. Write the SYMBOL of the element.
2. How many valence electrons does the element
have? (What group is it in?)
3. Start at 12:00 with your first dot
4. Add dots at 3:00, 6:00, and 9:00 moving
clockwise until you reach the correct number of
valence electrons.
• You need one dot at each location before you start
adding your second round of dots
**These rules are guidelines, not exact. Some conventions go
counterclockwise, others draw the structure exactly the same
for all group elements. The structure is fluid, it can be
rearranged to set up the element for bonding.
Practice

Draw the Lewis Dot Diagram for Phosphorus




P
Chemical Symbol: ____
15
Atomic Number: _____
30.974
Atomic Mass: ____
15
• Protons: ____
16
• Neutrons: _____
15
• Electrons: _____
5
# of Valence Electrons: _______
Practice

Draw the Lewis Dot Diagram for Fluorine




F
Chemical Symbol: ____
9
Atomic Number: _____
18.998
Atomic Mass: ____
9
• Protons: ____
10
• Neutrons: _____
9
• Electrons: _____
7
# of Valence Electrons: _______
Connection to Bonding
 Lewis
Dot Structures help in Bonding two or
more elements together to form compounds.
You can see the bonds in Lewis Dot form, or
using bonding structures with lines as shown
in the examples below. Each line represents
2 electrons.