1. Learning Objective
To be able to:
Describe how a covalent bond is formed, including bond diagrams
Key Words:
Sharing, electrons, dot-cross

2. Exam question Saturday, 25 May 2019 Ionic Bonding
Date and title in books. You need a pen, pencil & ruler.
Starter Activity – 5 minutes
Exam question

3. Draw diagrams to represent a covalent bond
(F)
Target 9-1
Identify why not all atoms bond ionically
(F/H)
Target 4-9
Describe a covalent bond
(H)
Target 5-9
Draw diagrams to represent a covalent bond
Extension: Application of Knowledge
Target 8/9
Describe the limitations of different ways of drawing a covalent bond
Learning Outcomes

4. Boardworks GCSE Additional Science: Chemistry Covalent Bonding
What is a covalent bond?
Non-metal elements usually just need one or two electrons to fill their outer shells. So how do they form a bond?
incomplete outer shells Cl Cl
The two non-metal atoms cannot form a bond by transferring electrons from one to another. Instead, they share electrons. Cl
Each atom now has a full, stable outer shell.
The shared electrons join the atoms together. This is called a covalent bond.

5. How is a covalent bond drawn?
Boardworks GCSE Additional Science: Chemistry
Covalent Bonding
How is a covalent bond drawn?
A covalent bond consists of a shared pair of electrons.
Covalent bonds are a result of electrostatic attraction between the positively-charged nuclei of the atoms and the negatively-charged shared electrons. Cl Cl
covalent bond
Only outer shells of electrons are involved in bonding, so the inner shells do not always have to be included in diagrams. Two common ways to represent a covalent bond are:
This information is higher tier for OCR Gateway GCSE Additional Science. The information about the electrostatic attraction is higher tier for OCR Twenty-first Century GCSE Additional Science.
simplified dot and cross diagram Cl
solid line Cl –

6. What are the types of covalent bonds?
Boardworks GCSE Additional Science: Chemistry
Covalent Bonding
What are the types of covalent bonds?
Teacher notes
This three-stage animation shows how covalent bonds form between atoms of different elements. While showing the animation, the difference between single, double and triple bonds could be pointed out.
The information about the covalent bonding in oxygen is higher tier for Edexcel GCSE Additional Science.

7. Which do I need to know?
You need to be able to draw dot-cross diagrams for:
Hydrogen (H2)
Chlorine (Cl2)
Oxygen (O2)
Nitrogen (N2)
Hydrogen chloride (hydrochloric acid, HCl)
Water (H20)
Ammonia (NH3)
Methane (CH4)

8. Limitations
What are the limitations to each of these diagrams showing a covalent bond?