Lewis Dot Diagrams

Visualizing valence electrons and how atoms bond to form molecules and compounds

CAPS Grade 10 Physical Sciences

Lewis Dot Diagrams are a simple way to represent valence electrons and predict how atoms will bond. They are essential for understanding chemical bonding and molecular structure.

1. Determining Valence Electrons

Definition: Valence electrons are the electrons located in the outermost energy level of an atom. These electrons play a critical role in chemical bonding.

Periodic Table Link

The group number of an element indicates how many valence electrons it possesses:

Group 1

Li, Na, K

Group 2

Be, Mg, Ca

Group 13

B, Al

Group 14

C, Si

Group 15

N, P

Group 16

O, S

Group 17

F, Cl

Group 18

Ne, Ar

Find the Valence Electrons

Click on an element to see its valence electrons:

Oxygen (O) Carbon (C) Sodium (Na) Chlorine (Cl) Magnesium (Mg) Nitrogen (N)

Click an element to see its valence electrons

2. Drawing Atomic Lewis Diagrams

The Octet Rule: Atoms tend to bond in ways that give them eight valence electrons (or two for hydrogen), achieving a stable electron configuration.

Placement Rules

Place one dot on each of the four sides (top, right, bottom, left) first.
After each side has one dot, pair dots on any side for additional electrons.

Interactive Lewis Diagram Builder

Use the buttons to add electrons to Carbon (C):

Valence electrons: 0/4

Examples

Hydrogen (H)

H•

1 valence electron

Oxygen (O)

:Ö:

6 valence electrons

Nitrogen (N)

:N:

5 valence electrons

Chlorine (Cl)

:Cl:

7 valence electrons

3. Lewis Diagrams for Covalent Bonding

Shared Pairs

In covalent bonding, atoms share pairs of electrons. Each shared pair is represented by a line.

H• + •H → H—H

Lone Pairs

Lone pairs are valence electrons not involved in bonding, shown as dots.

:Ö—H | H

Single, Double, and Triple Bonds

H H

Single Bond (H—H)
2 shared electrons

Double Bond (O=O)
4 shared electrons

Triple Bond (N≡N)
6 shared electrons

Standard Molecules

Water (H₂O)

Lewis Diagram:

H—Ö—H

with two lone pairs on O

Couper Notation:

H—O—H

Carbon Dioxide (CO₂)

Lewis Diagram:

O=C=O

Couper Notation:

O=C=O

4. Lewis Diagrams for Ionic Bonding

Electron Transfer: In ionic bonding, electrons are transferred from a metal to a non-metal.

Sodium Chloride (NaCl)

•

Sodium atom

1 valence electron

→

••• •••

Chlorine atom

7 valence electrons

↓

[ Na ] ⁺

Sodium ion

no dots (lost electron)

[ Cl •••••••• ] ^-

Chloride ion

8 valence electrons (octet)

Magnesium Oxide (MgO)

••

Magnesium atom

2 valence electrons

→

••••••

Oxygen atom

6 valence electrons

[ Mg ] ²⁺

[ O •••••••• ] ^2-

Match the Ions

Click on the correct ion representation:

Na⁺

Cl⁻

5. Transition to Couper Notation

In Couper notation, a shared pair of electrons is represented as a single line (—) in a structural formula. This simplifies the representation of molecules.

Molecule	Lewis Diagram	Couper Notation
Water (H₂O)	H—Ö—H (with lone pairs)	H—O—H
Methane (CH₄)	H—Ċ—H (with H above/below)	H—C—H (tetrahedral)
Ammonia (NH₃)	H—Ņ—H (with lone pair)	H—N—H (pyramidal)
Carbon dioxide (CO₂)	O=C=O	O=C=O

Convert to Couper Notation

The Lewis diagram shows H—Ö—H with two lone pairs. What is the Couper notation?

Key Terms

Valence electrons Octet rule Lewis dot diagram Lone pair Shared pair Single bond Double bond Triple bond Covalent bonding Ionic bonding Electron transfer Couper notation

Key Takeaways

Valence electrons are in the outermost shell - group number tells you how many
Octet rule: atoms bond to achieve 8 valence electrons (2 for hydrogen)
Lewis diagrams show valence electrons as dots around the element symbol
In covalent bonding, electrons are shared - shown as lines between atoms
Single bond (—) = 2 shared electrons, double bond (=) = 4, triple bond (≡) = 6
Lone pairs are non-bonding electrons shown as dots
In ionic bonding, electrons are transferred - ions shown in brackets with charge
Couper notation simplifies Lewis diagrams by using lines for bonds

Chemical Bonding Three Main Types of Bonding