Chemical Bonding 'O' Levels PDF

DARRELL ER (COPYRIGHTED) © DARRELL ER (COPYRIGHTED) TOPIC 2.3 - 2.6: CHEMICAL BONDING 1  DARRELL ER (COPYRIGHTED) © THE ABOUT Important chapter, will always be tested...

DARRELL ER (COPYRIGHTED) © DARRELL ER (COPYRIGHTED) TOPIC 2.3 - 2.6: CHEMICAL BONDING 1  DARRELL ER (COPYRIGHTED) © THE ABOUT Important chapter, will always be tested 3 key concepts 1 advanced concept TIME CHAPTER Commonly tested, especially for Section A ANALYSIS EXAM Tested as together with other chapters  Atomic Structure, Chemical Equations Medium overall weightage Constitute to 4.5% of marks for past 5 year papers WEIGHTAGE 2  ELEMENTS, COMPOUNDS, MIXTURE Elements Compound Mixture Formation Naturally found Combined using chemical methods Combined using physical methods Separation Cannot be separated further Separation by chemical methods Separation by physical methods technique (Decomposition, electrolysis, reduction with carbon) (separation techniques) Composition Exist by itself or in diatomic Fixed ratio Any ratio molecule form for gases such as H2 or O2. Melting Point / Fixed MP & BP Fixed MP & BP Melts and boils over a range of Boiling Point 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. Understanding the term An element can also exist as a diatomic molecule. (N2, O2, H2) ‘molecule’ 3 A compound is defined as 2 or more elements chemically combined, hence a compound must be a molecule.  ELEMENTS, COMPOUNDS, MIXTURE *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. Understanding the term An element can also exist as a diatomic molecule. (N2, O2, H2) ‘molecule’ 4 A compound is defined as 2 or more elements chemically combined, hence a compound must be a molecule.  DARRELL ER (COPYRIGHTED) © COVALENT 3 types of bonds 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 IONIC - The dot-&-cross diagram - The structure METALLIC - Physical properties (with explanations) 5  DARRELL ER (COPYRIGHTED) © MUST KNOW BASICS 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  DARRELL ER (COPYRIGHTED) © KEY CONCEPT IONIC BONDS METAL ION + NON-METAL ION GIANT IONIC LATTICE STRUCTURE 7  DARRELL ER (COPYRIGHTED) © Recall: Cation: positively charged ion  t = ‘+’ sign, positive Anion: negatively charged ion KEY CONCEPT IONIC BONDS  n = negative Ionic bonds are formed between metals and non-metals. The transfer of electron from the metal to the non-metal would allow both atoms to have complete valence shells and to attain a stable electronic configuration. The metal would become a cation while the non-metal would become the anion. Ionic bond formed is the forces of attraction between oppositely charged ions. 8  DARRELL ER (COPYRIGHTED) © GIANT IONIC LATTICE STRUCTURE Ionic compounds have a giant ionic lattice structure that is held together by strong electrostatic forces of attraction between oppositely charged ions. Naming convention: (Cation)(Anion) eg: Sodium Chloride GIANT IONIC LATTICE 9 STRUCTURE  DARRELL ER (COPYRIGHTED) © ADVANCED High melting and boiling points Ionic compounds usually have high melting and boiling points. (