[CHEM] Chapter 2.3 - 2.6 - Chemical Bonding

1 DARRELL ER (COPYRIGHTED) TOPIC 2.3 - 2.6: CHEMICAL BONDING DARRELL ER (COPYRIGHTED) ©

2 CHAPTER ANALYSIS THE ABOUT TIME EXAM WEIGHTAGE • Important chapter, will always be tested • 3 key concepts • 1 advanced concept • Commonly tested, especially for Section A • Tested as together with other chapters  Atomic Structure, Chemical Equations • Medium overall weightage • Constitute to 4.5% of marks for past 5 year papers DARRELL ER (COPYRIGHTED) ©

3 ELEMENTS, COMPOUNDS, MIXTURE Elements Compound Mixture Formation Naturally found Combined using chemical methods Combined using physical methods Separation technique Cannot be separated further Separation by chemical methods (Decomposition, electrolysis, reduction with carbon) Separation by physical methods (separation techniques) Composition Exist by itself or in diatomic molecule form for gases such as H2 or O2. Fixed ratio Any ratio Melting Point / Boiling Point Fixed MP & BP Fixed MP & BP Melts and boils over a range of temperature *A compound is a subset of a molecule, but a molecule does not need to be a compound. Definition of a molecule is when 2 or more atoms chemically combined. An element can also exist as a diatomic molecule. (N2, O2, H2) A compound is defined as 2 or more elements chemically combined, hence a compound must be a molecule. Understanding the term ‘molecule’

*A compound is a subset of a molecule, but a molecule does not need to be a compound. Definition of a molecule is when 2 or more atoms chemically combined. An element can also exist as a diatomic molecule. (N2, O2, H2) A compound is defined as 2 or more elements chemically combined, hence a compound must be a molecule. 4 ELEMENTS, COMPOUNDS, MIXTURE Understanding the term ‘molecule’

5 3 types of bonds IONIC COVALENT METALLIC Understanding all 3 types of bonds is needed to master this chapter while paying special attention to keywords you must include in your answers. For each type of bond, you must be able to explain: - How the bond is formed - The dot-&-cross diagram - The structure - Physical properties (with explanations) DARRELL ER (COPYRIGHTED) ©

Why are chemical bonds formed? Atoms of elements strive for stability by achieving a stable electronic configuration (2,8,8). This is by forming chemical bonds with other atoms. The formation of chemical bonds can be done by transferring electrons, sharing electrons or forming a metal lattice. Non-metal atoms, such as the Group VII halogens, would form ionic bonds with metal atoms. They can also form covalent bonds with other non-metal atoms. Metal atoms can also form metallic bonds with other metal atoms. 6 BASICS MUST KNOW DARRELL ER (COPYRIGHTED) ©

7 IONIC BONDS METAL ION + NON-METAL ION GIANT IONIC LATTICE STRUCTURE KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

Recall: Cation: positively charged ion  t = ‘+’ sign, positive Anion: