Grade 10 Academic Science - Chemistry
Elemental Notation
Each atom has an atomic number and atomic mass. The atomic number represents the
number of protons in the nucleus AND it is the atomic number that determines the identity of the
element. The atomic mass number represents the total number of protons plus the number
neutrons in an atoms nucleus.
As shown, the carbon atom has an atomic number of 6 and an atomic mass
number of 12. Thus, carbon has six protons and six neutrons.
Protons have a positive charge, electrons are negative and neutrons have no charge. Since the
atom has an overall neutral charge, the number of protons must equal the number of electrons.
Task – Complete the following table using the Periodic Table in your textbook.
Elemental
Notation
Sr
Number of
Protons
3
Number of
Electrons
3
Number of
Neutrons
4
Br
Na
Ne
O
Ba
Grade 10 Academic Science –Chemistry
Lewis Dot Diagrams
Lewis Dot Diagrams are very useful. With them, you can (1) determine the type(s) of covalent
bonds that an element may make, and (2) predict the type of ion that an atom might make.
Each dot diagram consists of an elemental symbol (called the kernel) and a group of 1-8 dots
which shows the configuration of the outer-most electron shell of the atom (i.e., the valence shell).
This is an example of the proper Lewis dot diagram for the element oxygen.
The "O" represents the kernel (the nucleus and all of the electrons except
those in the valance shell). Each of the four "sides" of the symbol represents
an orbital in the outermost energy level of the atom. Since each orbital can
hold only two electrons, the sides of the dot diagram can only hold up to two
dots. The six dots show the configuration of the valence electrons.
To make a Lewis Dot Diagram
Step 1

Step 2

. .
X X
.

You need to know how many electrons are in the valence
shell.
You fill in one valence electron on each side of the
elemental symbol, and then double up as many sides as
you need to in order to include each one.
Each side can only hold up to two dots.
By looking at the Lewis Dot Diagram for oxygen, you can see
that oxygen has two unpaired electrons, so it has two electrons
available for standard bonds. These unpaired electrons might
make two single covalent bonds (e.g., water (H2O)) or they
might make one double covalent bond, as the case of
magnesium oxide (MgO).
When Lewis dot diagrams are used to illustrate
compounds, "x's" are often used to substitute for the
dots of one or more elements to show which electrons
came from which element.
For example, the Lewis Dot Diagrams for both oxygen
and hydrogen as free elements, and then, water as a
compound.
Task – Draw the Electron Configuration and Lewis Dot Diagram for the following elements
Magnesium
Electron Configuration
Lewis Dot Diagram
Aluminum
Electron Configuration
Lewis Dot Diagram
Phosphorus
Electron Configuration
Lewis Dot Diagram
Argon
Electron Configuration
Lewis Dot Diagram
Boron
Electron Configuration
Lewis Dot Diagram
Carbon
Electron Configuration
Lewis Dot Diagram
Neon
Electron Configuration
Lewis Dot Diagram
Nitrogen
Electron Configuration
Lewis Dot Diagram
Sodium
Electron Configuration
Lewis Dot Diagram
Fluorine
Electron Configuration
Lewis Dot Diagram