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

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

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

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.

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 –

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.

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)

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